Macaron Shells
Separate egg whites 24 hours in advance, cover, and refrigerate. Bring to room temperature before using.
Line baking sheets with parchment paper or silicone mats. Prepare a piping bag fitted with a round tip.
Pulse pistachios with powdered sugar until very fine.
Sift pistachio mixture with almond flour; discard large bits.
Whip egg whites with cream of tartar until foamy. Gradually add granulated sugar.
Continue whipping to stiff, glossy peaks. Add vanilla and food coloring if using.
Gently fold dry ingredients into meringue using the macaronage technique until batter flows like slow lava.
Pipe 1½-inch rounds onto prepared trays.
Tap trays firmly to release air bubbles.
Rest shells 30–45 minutes, until dry to the touch.
Bake at 300°F (150°C) for 14–16 minutes, rotating halfway.
Cool completely before removing and pairing shells by size.
Pistachio Ganache
Heat cream until just steaming.
Pour over white chocolate; let sit 1 minute.
Stir until smooth, then mix in pistachio paste and salt.
Chill until thick but pipeable.
Pipe ganache onto one shell and sandwich with another.