For the black raspberry Swiss meringue buttercream frosting
1 ½cupssuperfine sugar
1cupunsalted butter, room temperature
⅓cupblack raspberry jam (or any flavor desired)
For the cookies
Preheat oven to 325°F.
In the bowl of an electric mixer, mix egg whites, vanilla, and almond extract on medium until they turn foamy. Add cream of tartar and whisk to soft peak stage. Reduce speed and slowly add baker’s sugar. Increase the speed to high and whisk until stiff peaks form.
In a separate bowl, sift almond flour and confectioner’s sugar through a fine-mesh sifter. This is an important step and while it takes extra time, it is needed to ensure a great cookie.
Sift almond flour and sugar a second time on top of the whipped egg whites. Gently fold whites and dry ingredients together until completely incorporated and the mixture looks smooth and shiny.
Pour into a pastry bag and use a ½-inch tip or cut bag to ½-inch opening. Pipe cookies approximately ¾-inch each on parchment-lined baking pans. Tap pans on counter to release any air bubbles and let the cookies rest for 15-30 minutes. The cookies need to dry slightly on top in order to bake correctly and should be dry to the touch.
Bake for 10-12 minutes. The cookies will puff up and become firm and crisp, but should not turn brown. Let cool on pans then remove them to a wire rack. Let oven heat back to 325°F between each batch.
For the buttercream frosting
Heat sugar and egg whites in a double boiler until the sugar is completely dissolved (approximately 160°F). Remove and whisk in an electric mixer on high, adding in vanilla until stiff peaks form, about 8-10 minutes. The whites will also cool off during this period.
Once at stiff peaks, add butter one tablespoon at a time, making sure to let each tablespoon fully incorporate before adding another.
Once butter is incorporated, fold in jam by hand.
To assemble the cookies, put buttercream in a pastry bag and pipe one tablespoon on the back of one cookie. Place another cookie on top.