Set oven to 300°F (150°C). Line baking sheets with parchment or silicone mats for even baking and easy removal.

Sift almond flour and powdered sugar together. This removes lumps and creates smooth, delicate macaron shells.

Use an electric mixer to beat egg whites with cream of tartar. Whip until soft peaks form, then gradually add granulated sugar.

If desired, add green food coloring to egg whites. Mix gently until evenly colored without deflating the meringue.

Carefully fold almond flour mixture into meringue using a spatula. Mix until smooth but do not overmix, to keep air in the batter.

Transfer batter to a piping bag. Pipe small circles onto baking sheets, spacing them evenly. Tap the tray to remove air bubbles.

Let piped shells rest at room temperature for 20–30 minutes. They form a thin skin on top for smooth, shiny macaron tops.

Bake in preheated oven for 18–20 minutes. Oven times may vary. Shells should be firm and slightly springy to the touch.

Remove shells from oven. Let them cool completely before removing from parchment. This prevents sticking or cracking.

Beat butter until creamy. Add powdered sugar, ground pistachios, and vanilla. Mix until smooth. Add milk if needed for spreading consistency.

Pipe or spoon pistachio filling onto half of the shells. Top with remaining shells, gently pressing to form sandwiches.

Refrigerate macarons for at least one hour before serving. This improves texture and flavor by allowing shells and filling to meld.