1. Line two baking sheets with parchment paper or silicone mats and prepare a piping bag with a round tip.

2. Sift the almond flour and powdered sugar together into a bowl and discard any large bits.

3. In a clean mixing bowl, beat the egg whites until foamy, add the cream of tartar, then slowly add the granulated sugar and whip until stiff glossy peaks form.

4. Mix in the peppermint extract and gel food coloring until evenly combined.

5. Fold the dry ingredients into the meringue in batches until the batter flows slowly like thick ribbon and settles back into itself after a few seconds.

6. Pipe small circles onto the prepared trays, tap the trays on the counter to release air bubbles, and pop any visible bubbles with a toothpick.

7. Let the shells rest at room temperature for 30 to 60 minutes, or until the tops feel dry to the touch.

8. Bake one tray at a time at 300°F for 14 to 16 minutes, then cool completely before removing the shells.

9. Beat the butter until creamy, then add the powdered sugar, peppermint extract, and enough heavy cream to make a smooth pipeable filling.

10. Fold crushed peppermint candies into the filling if desired.

11. Match the cooled shells by size, pipe filling onto half of them, and sandwich with the remaining shells.

12. Refrigerate the assembled macarons for 24 hours for the best texture, then bring to room temperature before serving.