week 4. blueberry macs x lemon blueberry buttercream

using my base recipe, I subbed out cocoa powder for the equivalent amount of almond flour and finely ground dried blueberries to flavor it.

this was the first week that I was not super happy with the appearance of my macs. all but 8 of the shells had major cracks on top. this was also the first time I added a couple drops of gel food coloring, so it's possible that had something to do with it. it's also possible that I over-mixed the batter. either way, they taste amazing, so I would absolutely try this recipe again. I would instead add a dab of food coloring to the buttercream so that it matched the purple shells a little better instead of turning out so pink. these definitely have a 90s southwestern vibe to them that I could do without.

ingredients | shells

mixture a:
freeze-dried blueberries
-finely ground                                             18g
almond flour                                                19g

almond TPT*                                                300g
powdered sugar                                        38g

egg whites                                                      73g          

mixture b:
egg whites                                                      73g
salt                                                                       0.5g
water                                                                  50g
sugar                                                                  188g
light corn syrup                                          10g

* TPT means equal parts powdered sugar and another ingredient, in this case it’s almond flour, and you will use 150g of each to equal the 300g.

method | shells

bring all ingredients to room temperature.

use a blender (vitamix does a great job) to grind the freeze-dried blueberries until it becomes a fine powder.

from “mixture a,” sift together the blueberry powder, almond flour, almond TPT, and powdered sugar into a large bowl and set aside. (it’s important to sift to make sure everything is very fine).

from “mixture b” whisk the egg whites and salt in a standing mixer with the whisk attachment set to 4 and leave it there while you make a syrup.

make a syrup from “mixture b.” first add the water, then the sugar, then the corn syrup into a small saucepan. pour the sugar in very slowly so that it all gets incorporated into the water, being very careful not to get any on the sides of the saucepan or your syrup can crystallize. do not stir!! stirring can also cause crystallization. just let it do its thing.

heat this syrup on medium until it boils and reaches 248°F. really, don’t stir it!

tip: you can take the chill off the eggs if you hold the bowl over the heating saucepan for a few seconds while swirling it around or stirring it.

turn up the standing mixer to 8 to create soft peaks while the syrup is still heating up to the right temperature.

to create the meringue, slowly pour the hot syrup along the side of the bowl into the mixing egg whites and let it mix until it’s stiff, but still shiny.

take the egg whites from “mixture a,” plus a spatula full of the meringue and mix it into the sifted almond, blueberry powder, powdered sugar mixture that you made earlier. fold this together with a spatula until you form a thick paste.

fold the rest of the meringue into that paste until it becomes glossy and slightly runny. (you’ll know when it’s done when the batter slowly falls off your spatula like a thick ribbon and settles into itself in the bowl after a few seconds. you don’t want it to be any runnier than that because you don’t want the mixture to spread once it’s piped).

scoop batter into a pastry bag fitted with about a 10mm piping tip, and pipe quarter sized bulbs onto parchment paper or a silicone baking mat on a sheet pan.

tip: if a little nub from where you released the piping bag doesn’t settle into itself, you can use a small paintbrush to tap it down.

tap the bottom of the pan a couple times to prevent any air bubbles while baking.

bake on your oven’s convection setting at 280° for 15 minutes. for the first 5 minutes with the oven door closed, and the remaining 10 minutes with a wooden spoon propping the oven door open a bit.

let cool completely before filling.

ingredients | lemon blueberry buttercream

butter                                                                1/2 cup
powdered sugar                                        1 cup
vanilla extract                                              1/2 tsp

lemon curd                                                   1/4 cup
blueberry powder                                    2 heaping tbsp
gel food coloring*                                     1-2 drops (optional)

* I would next time use some blue or purple food coloring to better match the shells. this buttercream turned out really pink.

method | lemon blueberry buttercream

in the bowl of a standing mixer, fitted with the paddle attachment, cream the butter until creamy.

add in the vanilla extract and mix for about 30 more seconds, then add in powdered sugar and mix on the "stir" setting until incorporated, then up the speed to about 6 for about a minute.

add in your blueberry powder, lemon curd, and food coloring (if you decide to use it) and whip on 6 for another minute.

spread or pipe buttercream on your shells and sandwich together.

store in the refrigerator for up to a week.

tip: the sizes of all of your shells will tend to be slightly different, so make sure you buddy up your shells to similarly sized partners so that the entire cookie is a consistent size.