PREP AND SIFT DRY INGREDIENTS: In a large bowl, sift the almond flour and powdered sugar together twice to remove any lumps and create a very fine mixture.
WHIP THE EGG WHITES: Place room-temperature egg whites in a clean, grease-free mixing bowl. Add a pinch of salt or cream of tartar for stability. Beat on medium speed until foamy, then gradually add the granulated sugar. Increase to high speed and continue whipping until stiff, glossy peaks form, about 6–8 minutes.
MACARONAGE (FOLDING): Add the sifted dry mixture to the meringue in three parts. Fold gently with a spatula by scraping around the bowl and through the center. The batter should flow slowly and look glossy. When lifted, it should ribbon back into the bowl and disappear within about 10 seconds.
PIPING AND RESTING: Transfer the batter to a piping bag fitted with a round tip. Pipe 1.5-inch rounds onto a baking sheet lined with parchment paper or a silicone mat. Tap the tray firmly on the counter to release any air bubbles. Let the shells rest for 30–60 minutes until a dry skin forms on the surface and they no longer stick to your finger when touched lightly.
BAKING: Preheat the oven to 150°C (300°F). Bake the macarons for 15–18 minutes until they have developed feet and the tops are set without browning. Allow them to cool completely on the tray before attempting to remove.
MAKING THE FILLING: In a mixing bowl, beat the butter until light and creamy. Gradually add the powdered sugar, then mix in the vanilla extract and salt. Add cream or milk 1 tablespoon at a time until the frosting reaches a smooth and pipeable consistency.
ASSEMBLE THE MACARONS: Match similar-sized shells into pairs. Pipe a small dollop of buttercream in the center of one shell and gently press the second shell on top to form a sandwich. Repeat with all remaining shells and filling.
PAINTING THE FIREWORKS: Mix each gel food coloring with a few drops of vodka or clear extract to create a paint-like consistency. Using a clean, food-safe brush, paint short, outward strokes from the center of each shell to create a firework burst. Allow the designs to dry completely before serving or storing the macarons.