01 - Line two baking sheets with parchment paper or silicone mats. Fit a pastry bag with a 1/2-inch round tip.
02 - Sift almond flour and powdered sugar together into a bowl. Set aside.
03 - In a clean, dry bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add granulated sugar, beating until stiff, glossy peaks form.
04 - Gently fold almond flour mixture into meringue in three additions. Tint one-third of batter yellow if desired. Mix until batter flows in thick ribbons (macaronage stage).
05 - Transfer batter to pastry bag. Pipe 32 rounds (1.5 inches each) onto prepared sheets. Tap trays firmly on counter to release air bubbles.
06 - Let shells rest 30-60 minutes until surfaces are dry to touch. Preheat oven to 300°F. Bake 13-15 minutes, rotating pans halfway. Shells are done when they lift easily from mat. Cool completely.
07 - Heat cream until simmering. Pour over chopped milk chocolate and let stand 2 minutes. Stir until smooth. Add golden syrup and butter, mixing until glossy.
08 - Reserve one-quarter of filling and tint with yellow gel coloring. Chill both fillings until thickened to pipeable consistency.
09 - Pipe a ring of chocolate filling on one shell. Place a dollop of yellow filling in center. Top with another shell. Repeat with remaining shells.
10 - Store assembled macarons in airtight container overnight to mature flavors. Refrigerate up to 5 days.