Kaffir Lime Macarons

KAFFIR LIME GERMAN BUTTERCREAM

1. In a bowl, whisk together the sugar, corn starch, egg, egg yolk and salt. In a medium non-stick saucepan, heat the milk, the 8 chopped kaffir lime leaves and vanilla to just shy of a simmer.  Remove from the heat.
2. Using one hand to whisk constantly, pour half of the hot milk mixture into the egg mixture. This helps to temper the eggs and stop them from scrambling. Whisk until incorporated, and then pour the whole lot back into the saucepan.
3. Heat the milk and egg mixture over medium heat, whisking constantly, until it begins to bubble. It will thicken quickly. Once it has thickened, cook for one minute, then remove from the heat. Pour into a shallow dish or bowl of a stand mixer and press some plastic wrap over the surface to avoid a skin from forming. Refrigerate until cold - at least four hours, preferably overnight.
4. Fit your mixer with the whisk attachment. Pass the pastry cream through a sieve in order to remove any lime leaves. Whip the mixture on medium until creamy and lump-free. Begin adding the butter, a few cubes at a time, until fully incorporated. It may look curdled at some point but just keep whipping - it will come together!
5. Place the remaining 2 chopped Kaffir lime leaves and the 2 Tbsp sugar in a mortar and pestle or spice grinder, and process until finely ground. Add to the buttercream.

MACARONS

1. Preheat oven to 300˚f / 150˚c, and position the oven rack in the centre of the oven. Using a round cookie cutter or the base of a large piping tip (something about 1.5 inches in diameter), draw a "template" for your macarons on a piece of parchment paper, leaving about ¾" between each circle.
2. Place the ground almonds and powdered sugar in the work bowl of a food processor, and pulse until it resembles very fine crumbs. Sift twice through a sieve, discarding any chunks, and set aside. If there are a large number of chunks, return to the food processor and pulse again.
3. In the bowl of a stand mixer fitted with the whisk attachment, whip the egg whites on medium speed until foamy. Gradually add the sugar, increase the mixer speed, and whip on high until the meringue starts to firm up. Add green gel food colour a few drops at a time, until the desired colour is reached. Add vanilla and mix until incorporated. Continue to whip until the meringue forms stiff peaks (there is a good example here).
4. Remove the bowl from the mixer. Add half of the ground almond and powdered sugar mixture, and fold into the meringue. You want to deflate the meringue just a little at this stage, to combine the meringue and ground almond mixture.
5. Add the remaining ground almond mixture, and stir lightly to combine. Now comes the important part - mixing the batter to the correct consistency. Again, this video does a good job of explaining it. Fold the mixture in a series of 'turns', deflating the batter by spreading it against the side of the bowl. Turn the bowl slightly and repeat the movement - scooping the batter from the bottom of the bowl, and spreading it against the side. Continuously check the consistency of the batter - you want it to flow like lava when you lift the spatula from the bowl, and you should be able to 'draw' a figure 8 with it, without the batter breaking (again, watch lots of videos to get an idea! They help so much). This step can take some practice until you know what it should feel and look like. If in doubt you are better to under mix them than over mix them - the process of putting the batter into the bag and piping out will help mix a little too.
6. Fit a large pastry bag with a medium sized round tip, such as an ateco #805. Place the macaron template on a sheet pan, and place a second piece of parchment over it. Holding the piping bag at a 90˚ angle to the surface, pipe out the batter into blobs the size of the circles drawn on the template. Finish off each piped circle with a little "flick" of your wrist to minimise the batter forming a point (it will still form a small one, but we can get rid of this with banging). Remove the template from under the macarons.
7. Hold the baking sheet in two hands, and carefully but firmly, evenly bang it against the bench. Repeat this a few more times - this will get rid of any air bubbles, remove points on the top, and help them to spread out slightly.
8. Repeat the piping and banging process until you have used up all of the batter - I usually make three sheet pans worth.
9. Allow the macarons to dry at room temperature for approximately 30 minutes, or until they form a skin that you can touch without your finger sticking to them. This time will drastically vary depending on the humidity.
10. About fifteen minutes before you are going to bake the macarons, place a spare sheet pan in the oven to preheat - this is going to be used to place under the pan with the macarons on it, to double up, which should help with even baking. Bake the macarons one sheet at a time - place the sheet with the macarons on the preheated sheet, and place in the oven.
11. Bake for approximately 18 minutes, rotating the pan once during the cooking process, and checking for doneness after 15 minutes. The macarons should develop a foot (the ruffled part on the bottom of the macaron), and bake without browning. To see if they are done - press down lightly on a shell. If the foot gives way, it needs a little longer, if it is stable, then it is close to being done. Test a macaron shell - if you can peel it away cleanly from the paper, they are done. If they are stable but cannot yet peel away cleanly, give them another minute or so. Again, this part takes a little trial and error depending on your oven. If they seem done but do not peel away cleanly, do not worry - there is a little trick for that!
12. Remove from the oven, and allow to cool on the sheet pan for 10 minutes before peeling off the parchment paper and allowing to cool completely on a wire rack. Repeat the baking with the remaining trays, using the same spare sheet pan to double up.
13. If your macs do not peel away cleanly, place them, on the parchment paper, into the freezer for 5-10 minutes, then peel away from the paper.
14. Store cooled macarons in an airtight container until ready to use.

ASSEMBLY

1. Transfer the buttercream to a large piping bag fitted with a french star tip (such as an ateco #868). Match the macaron shells up so that they are in pairs of equal size.
2. Pipe a blob of buttercream on one half of the macaron, and place the second half on top, pressing lightly. Macarons are best after an overnight rest in the regrigerator. Bring to room temperature before eating.