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, whisk egg whites and cream of tartar until soft peaks form. Gradually add granulated sugar while whisking 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 when lifted.
05 - Transfer batter to pastry bag. Pipe 32 rounds, approximately 1.5 inches diameter, onto prepared sheets. Tap trays firmly on counter to release air bubbles.
06 - Let piped shells rest at room temperature for 30 to 60 minutes until surfaces are completely dry to the touch.
07 - Preheat oven to 300°F. Bake for 13 to 15 minutes, rotating pans halfway through. Shells are done when they easily lift from the baking mat. Cool completely.
08 - Heat heavy cream until just simmering. Pour over chopped milk chocolate and let sit for 2 minutes. Stir until smooth. Add golden syrup and butter, mixing until glossy.
09 - Reserve one-quarter of the filling and tint with yellow gel coloring. Chill both chocolate and yellow fillings until thickened to pipeable consistency.
10 - Pipe a ring of chocolate filling onto one shell. Place a small dollop of yellow filling in the center. Sandwich with another shell. Repeat with remaining macarons.
11 - Store assembled macarons in an airtight container overnight to allow flavors to mature. Refrigerate for up to 5 days.