Place the cocoa powder, confectioners’ sugar, and almond flour in a food processor or blender and pulse or blend for 30 seconds until thoroughly combined and fine in texture. Set aside.

In a completely dry and grease-free bowl, beat the egg whites and salt together on medium speed for 1 minute. Switch to high speed and beat *just* until stiff peaks form, about 3 minutes. Do NOT overbeat. Gently fold in the sifted granulated sugar, 1 Tablespoon at a time.

Using a metal spoon or rubber spatula, fold in the confectioners’ sugar/almond flour mixture until combined. Be very gentle and light-handed while doing so. Once completely combined, the mixture will be smooth, sticky, and glossy.

Let the batter sit uncovered at room temperature for 10-30 minutes. Meanwhile, fit your piping bag with the piping tip. Line 2-3 baking sheets with silicone baking mats—I find bare nonstick sheets and parchment paper difficult to work with; the macaron shells spread more and are harder to remove from the sheet.

Fill the piping bag with the batter and pipe evenly sized rounds onto the baking sheets—make sure you are holding the bag vertically and close to the baking sheet. While piping, the batter will slightly spread out, so keep that in mind. You want around 2-inch circles. Gently tap the bottom of the baking sheets on your counter to rid any large air bubbles. You can lightly sprinkle a few sprinkles, a dash of cinnamon, or any edible decorations onto the wet round shells at this point.

Let the piped rounds sit for at least 45 minutes and up to 1 hour. This is crucial to making macarons! The air will will help the rounds set and form a dry shell. They should not be sticky going into the oven.

Preheat oven to 325°F (163°C). Bake the macarons for 10 minutes, one baking sheet at a time. Rotate the pan at the 5 minute mark. The tops should be crisp and the macarons should have formed their signature crinkly “feet.” Allow to cool completely on the baking sheet before filling.

Using a handheld or stand mixer fitted with a paddle or whisk attachment, beat the peanut butter and butter together on medium-high speed until smooth. On low speed, mix in the confectioners’ sugar, vanilla, and salt. Increase to high speed and beat until light and creamy. Add 1-2 Tablespoons of milk to thin out, if desired.

Fill and sandwich two shells together to form the macaron cookie. Leftover macarons keep well covered at room temperature or in the refrigerator for up to 1 week. Any leftover filling? Cover tightly and store in the refrigerator for up to 5 days. It’s great on cupcakes.