Make the Macaron Shells:

1. Prepare Dry Ingredients: Sift the almond flour and powdered sugar together. Discard any large pieces. Set aside.
2. Whip Egg Whites: In a large bowl, beat egg whites on medium speed until foamy. Gradually add granulated sugar and increase to high speed until stiff peaks form.
3. Flavor & Color: Gently fold in the peppermint extract and red food coloring.
4. Combine: Fold the dry ingredients into the whipped egg whites in thirds. Mix until the batter flows like thick ribbons. Avoid overmixing.
5. Pipe: Fill a piping bag with the batter and pipe small circles (1.5 inches) onto a parchment-lined baking sheet.
6. Rest: Let the macarons rest at room temperature for 30–60 minutes until they form a skin that doesn’t stick when touched.
7. Bake: Preheat oven to 300°F (150°C). Bake for 15–18 minutes. Cool completely before removing from the baking sheet.

Make the Filling:

1. Beat softened butter until creamy.
2. Add powdered sugar gradually, mixing well. Stir in peppermint extract.
3. Adjust consistency with heavy cream or milk, one tablespoon at a time.

Assemble:

1. Pair similar-sized macaron shells.
2. Pipe a dollop of buttercream on one shell and sandwich it with another.
3. (Optional) Roll edges in crushed peppermint candies.
4. Store in an airtight container and refrigerate for 24 hours before serving.