Preheat the oven: Preheat your oven to 300°F (150°C). Line two baking sheets with parchment paper or a silicone baking mat.

1. Prepare the macaron shells: In a food processor, pulse together the powdered sugar and almond flour until very fine and smooth. Sift the mixture into a bowl to remove any lumps.
2. Whisk the egg whites: In a clean, dry bowl, beat the egg whites with an electric mixer on medium speed until soft peaks form. Gradually add the granulated sugar while continuing to beat on high speed until stiff peaks form.
3. Fold in the lavender and color: Gently fold the lavender extract and food coloring (if using) into the egg whites.
4. Fold in dry ingredients: Sift the almond flour mixture into the meringue in batches, being careful not to deflate the meringue. The mixture should flow like lava, smooth but not runny.
5. Pipe the macaron shells: Transfer the macaron batter to a piping bag and pipe 1-inch rounds onto the prepared baking sheets, spacing them about 1 inch apart. Tap the baking sheets on the counter to release air bubbles.
6. Rest the shells: Let the piped macaron shells sit at room temperature for 30-60 minutes, or until they form a skin that’s dry to the touch.
7. Bake the macarons: Bake for 12-15 minutes, or until the macarons have risen and developed a “foot” and are firm to the touch.
8. Cool the macarons: Let the macarons cool completely on the baking sheets before removing them.
9. Prepare the lavender buttercream: Beat the softened butter until creamy. Gradually add powdered sugar, heavy cream, and lavender extract (or syrup). Mix until light and fluffy, adding food coloring if desired.
10. Assemble the macarons: Once cooled, flip half of the shells over and pipe the lavender buttercream onto the flat side of each. Sandwich the shells together and press lightly.
11. Chill the macarons: Refrigerate the assembled macarons for at least 24 hours before serving to allow the flavors to meld. Bring to room temperature before serving.