March: Key Lime Pie Macarons

Today is Pi Day (which I always celebrate with pie, obviously), followed closely by St. Patrick’s Day later this week.  In tribute to both occasions, this month’s A Year in Macaron flavor embodies the fresh tartness of my favorite green-colored pie: Key Lime Pie Macarons!

In college, my friends and I would always embark upon a yearly quest for pie to celebrate March 14th.  We told ourselves that it was our moral obligation to honor π in all it’s mathematical glory and all thing circular.  In reality, it was just an excuse to traipse around Boston in search of a pie to devour later in the day.  We’d usually be able to collect a few flavor options among a group to enjoy as a study break; apple, berry, chocolate, pecan… you name it, we probably had it it some form or another.  I could usually get away with having a small sampling of each, but if there was ever a key lime pie present, I couldn’t help but go for seconds!  So here’s my tribute to all those second servings…

To call these macarons “key lime pie” might be a bit of a misnomer, as it in no way resembles pie nor did I have any Florida Key limes on hand.  Despite using your normal grocery store limes, this macaron certainly packs the unmistakable sweet-and-tart flavor of a classic key lime pie.  The filling consists of a simple homemade lime curd encircled by a fluffy vanilla swiss meringue buttercream.  This (along with the matcha green tea macarons) will easily become a St. Patrick’s Day classic!  

As I mentioned last month, I experimented with a new macaron shell recipe; I played around with the almond flour-confectioner’s sugar-caster sugar ratios to see if it would help with the “sunken shells” problem.  All done it unfortunately did not solve the problem, however, the texture of the macarons was enjoyably chewy and the hint of almond really shone through.  I just might continue using this new ratio, but still need to pinpoint what my issue is—next month I might just revert back to the hand mixer to whip up the meringue and see if that does the trick!  

Wish me luck and stay tuned for what April’s flavor will be :) In the meantime, wishing you a wonderful Pi Day and St Patrick’s Day!  

-E

PS: See my light version of mini key lime pie if you’re looking for a less time-consuming confection to make!

Key Lime Pie Macarons + Lime Curd Filling

2016-03-14 22:32:51

Yields 24

A delicate French almond cookie with a sweet and tart key lime curd filling encircled in a vanilla Swiss meringue buttercream. A refreshing treat!

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[Ingredients] Macaron Shell

1. 100 g egg whites, aged 3 days
2. 75 g caster sugar
3. 150 g confectioners sugar, sifted
4. 150 g almond flour, sifted
5. 1 pinch of salt
6. (optional) 2 drops gel food coloring, leaf green
7. (optional) 1 drop gel food coloring, lemon

[Ingredients] Key Lime Curd

1. 1 egg, beaten
2. 1/4 c key lime juice
3. 1/3 c granulated sugar
4. 2 tbs butter
5. 1 Tbs cornstarch
6. 2 tsp lime zest
7. (optional) 1 small drop gel food coloring, green leaf

[Ingredients] (Optional) Vanilla Swiss Meringue Buttercream

1. 1 egg white, large
2. 1/3 c sugar
3. 1/4 c butter unsalted, softened
4. 3/4 tsp vanilla extract

[Directions] Macaron Shell

1. Measure out dry ingredients using the food scale. Let egg whites sit until room temperature.
2. Meanwhile, pulse together powdered sugar and almond powder in food processor until well blended.
3. Meringue--In a very large bowl, whisk the room temperature egg whites, caster sugar, and salt into a meringue. I’ve found that it takes me about 7-9 minutes to completion, and I break it down into three basic steps: [1] Starting on a low-speed setting, whip the egg whites with an electric mixer for 2-3 minutes until frothy, adding ⅓ of the caster sugar and a pinch of salt along the way. [2] Move mixer to med-speed setting; continue whipping egg whites another 2-3 minutes until soft peaks form, and add half of the remaining caster sugar along the way. [3] Move mixer to high-speed setting; whip egg whites 1-2 minutes and add the remaining caster sugar and optional gel coloring along the way. Move mixer to highest speed for last minute until firm peaks form.
4. Be careful not to over beat the egg whites! You will know when your meringue is ready by checking to see if (a) nothing falls out of the bowl when you turn it upside down, and (b) the meringue remains in the whisk/beater when you stop the mixer.
5. Fold in the mixed and sifted dry ingredients into the meringue; this is the actual macaronage step. I find that it takes me anywhere from 40-50 folds (and I actually do keep count) to achieve the right consistency. Folding doesn’t require gentleness; the macaronage process requires one to “beat” out the air from the egg whites. When a shine develops and the consistency resembles lava or thick pancake batter, macaronage is complete. I’m careful to count the folds in order to not overmix!
6. Transfer macaron batter to a pastry bag fitted with a large round tip (I use the Ateco #11 round). Pipe even circles on prepped baking sheets lined with Silpat-like mats. For even circles, I count out 1-2-3-4 while piping to help ensure more even batter distribution for each circle. It’s not a foolproof solution, but it works surprisingly well! Alternatively, there are templates that can be used and placed under the Silpat-like mats for additional assurance.
7. Knock the air bubbles out! To prevent cracking and empty shells, the extra air bubbles have got to go! In parallel, drop the fully-piped baking sheet from a 4-6 inch range onto a counter or table that can withstand an impact. Do this three times, rotate the sheet 180-deg and do so three times again. It’s loud and might seem excessive, but seeing those tiny bubbles rise to the surface and pop make it all worth it.
8. Let the shells try in a dry place. The top coat of the shell should be dry to the touch; no batter should stick. This may take anywhere from 30-120 minutes. I tend to wait at least an hour to ensure a hardened shell. Drying the shell is required for a smooth shell and macaron feet to form without cracking. Bake too soon before the shells are dried and the shells will crack—I’ve had this experience once or twice before and it’s the last thing you want to happen after having invested so much work into preparing the shells leading up to the baking.
9. Pre-heat the oven to 325º F. Bake for 5 minutes before lower temperature to 300º F for the remaining 10-15 mins, rotating the sheet a touch more than halfway through the baking process after feet have formed. While I prefer to bake each sheet individually to exercise greater control over each, in the interest of time, I have tried baking both together (on middle/bottom rack and switching them halfway through) and have found success.
10. Remove shells from oven and let it cool completely before removing/peeling from the mat. Be sure to let them cool completely, as premature removal will result in decapitation—the “cap” of the macaron shell will literally come off, leaving the base/crinkly feet on the mat. No bueno :(
11. As shells bake/cool, prepare the key lime curd and buttercream fillings.

[Directions] Key Lime Curd Filling

1. In a double boiler (or in a bowl fitted over a pot of boiling water, which is what I did), heat lime juice, sugar, butter, cornstarch for 5-7 minutes, stirring occasionally; butter should be completely melted.
2. Remove from heat and whisk a quarter of the heated mixture into beaten egg to temper. Whisk egg mixture and lime zest into lime mixture and return to heat on double boiler.
3. Heat on medium for another 15-20 minutes, until mixture thickens.
4. Remove from heat and let cool to room temperature (can be placed in refrigerator to speed up cooling process).
5. Optionally fill a piping bag with cooled key lime curd.

[Directions] Vanilla Swiss Meringue Buttercream Filling

1. Bring a pot of water to a simmer on the stove.
2. In a stand mixer bowl, whisk together egg whites and sugar over the simmering water, being careful to not place the bowl directly on the water--we don't want to cook the egg white! As you mix, the sugar will dissolve in the egg white, resulting in a gel-like mixture; it should not feel gritty between your fingers. This step requires ~10 minutes of mixing over the water; you should aim to hit a temperature 140º F to pasteurize the egg white.
3. Fit the mixing bowl back into the stand mixer or use a hand mixer to beat the egg white-sugar mixture starting on med-low and progressing up to high until it forms stiff peaks and it has cooled to room temperature (as you beat and incorporate air, the mixture will cool).
4. Add in butter in 1 tablespoon chunks at a time on medium speed. Add in salt and vanilla extracts. Continue beating until blended together and smooth. If it looks like it's separating, don't freak out! Be patient as it will come together, I promise! And if you're not convinced, beat it on high and you'll see it start to take it's fluffy, creamy shape!
5. Fill the buttercream in a pastry bag fitted with a piping tip (#11 Ateco, I use the same one for the macarons) in preparation for assembly.

[Directions] Assemble Macarons

1. Sort and match macaron shells into pairs of roughly equal size.
2. For each cookie pair, optionally pipe a ring of buttercream on the perimeter of the flat side of one cookie. Pipe cooled key lime curd in the center of the cookie.
3. Place the accompanying cookie on top and optionally twist the cookies in opposite directions to help distribute the filling throughout the macaron, out to the edges. Repeat for remaining cookies.
4. You can now enjoy your the fruits of your labor immediately! Or... store assembled cookies in an air-tight container in the fridge for 12-24 hours. This allows the flavors to penetrate through the entirety of the macaron, enhancing both the texture and flavor of the eventual tasting experience!
5. To serve, remove from refrigerator and let the macarons warm to room temperature prior to enjoying. (Hint: if it's crunchy when you bite into it, it's probably still too cold)

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