Prepare a piping bag fitted with a medium round tip, like a #12, or with the tip of the bag cut off. To make the bag easier to fill, use a bag holder. Twist the piping bag above the tip and secure with a small binder clip to prevent batter from flowing out during filling. Set aside.
Sift together the oat flour and powdered sugar in a small bowl. Set aside.
126 grams oat flour, 126 grams powdered sugar
In the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites on medium-high speed.
100 grams egg whites at room temperature
Once the egg white are foamy, add the cream of tartar. Then, slowly add the granulated sugar, one spoonful at a time.
¼ teaspoon cream of tartar, 90 grams granulated sugar
Add the vanilla and food coloring and continue to beat until the meringue has formed stiff peaks.
1 teaspoon vanilla, orange food coloring gel
Remove the bowl from the mixer and carefully fold ⅓ of the flour mixture into the meringue. Then add the rest of the flour mixture. Continue folding and stirring until just before the figure 8 stage.
Transfer the batter to the piping bag and pipe 1-inch circles onto the macaron mat or parchment with 1-inch circles drawn on the under side of the paper.
Slam the tray on the counter several times to cause air bubbles to rise to the surface. Use a toothpick to pop any large bubbles and smooth batter over the hole.
Allow the batter to sit for 40 minutes to dry at room temperature before baking. Meanwhile, preheat the oven to 300°F.
Bake the Macaron Shells
Bake the macarons for 12-14 minutes, rotating once after 7 minutes.
Remove the cookies from the oven and allow them to cool completely on the mat before removing.
Assemble the Macarons
Because the macarons will be sandwiched, pair up the shells by size. You want the top and bottom of the sandwich cookie to match as closely as possible.
Add the buttercream to a piping bag with a round or decorative tip and pipe a large mound in the center of each bottom shell.
Carefully place the flat side of the top shell on top of the filling, pressing down slightly to adhere.
Decorate the Macarons:
Place a drop of black food coloring gel in the well of a food dedicated paint palette.
Place an assembled macaron in the center with the smoothest side facing up.
Dip a thin food grade paintbrush into the black gel and paint the outline of a Jack-O-Lantern face on the macaron shell. Then, use more gel to fill in the design.
Allow the food gel to dry before storing the cookies. Place the cookies in a single layer in an airtight container. Store in the refrigerator to mature. Allow the cookies to come to room temperature before serving.
Notes
I highly recommend weighing the ingredients listed in grams with a digital kitchen scale. French macarons are notoriously finicky and require precise measurements.Use cracked whole eggs, not store bought egg whites. 100 grams of egg whites (to make both green and pink shells) is the equivalent of the whites from about 3⅓ large eggs."Macaronage," the process of folding the dry ingredients into the meringue, is the trickiest step of macaron making. The batter will be too thick if you under mix it or too thin if you over mix it. I refer you to two resources with visuals as to when the batter is ready to be piped: America's Test Kitchen and Le Cordon Bleu.Easy Vanilla Buttercream recipe HEREStore the cookies in an airtight container in the refrigerator for a few days to allow them to mature and improve in texture. If refrigerated, allow the cookies to come to near room temperature before serving so the buttercream can soften. Unfilled shells or assembled macarons can be frozen.Nutritional information is only an estimate and will vary based on your ingredients and substitutions. For this recipe, the filling is not included in the calculation.You're Gonna Bake It After Allbakeitafterall.com