Heat oven to 350°F Line 24 regular-size (2 1/2-in. diam) muffin cups with paper or foil liners (see Note 2).
Spoon cake batter into lined cups, filling each 2/3 full. Bake as box directs. Transfer to a wire rack to cool completely. Using tip of a paring knife, cut a small hole in top of each cupcake.
Prepare custard as box directs, stir in grated peel and cool until warm. Spoon into a sturdy ziptop food bag, cut tip off one corner and pipe into holes in cupcakes (you’ll have about 1/2 cup custard left.) Insert a half orange section into custard in each cupcake. Refrigerate until serving.
Note 1: Look for Bird’s Imported English Dessert Mix in the pudding-mix section of your.
Note 2: Since the recipe makes 24 cupcakes, if you have two 12-cup, regular-size muffin pans you can prepare them both as the recipe directs and bake them side by side on the middle rack of your oven.
Can be prepared through Step 2 up to 2 days ahead. Complete up to 1 day ahead. Refrigerate covered.