Heat oven to 350°F. Place paper baking cups in each of 24 regular-size muffin cups. Make and bake cake mix as directed on box for cupcakes using water, oil and eggs; cool completely. Freeze 12 of the cupcakes for a later use.
With 1/2 cup of the frosting, frost remaining 12 cupcakes. Place 3 candy-coated chocolate pieces on center of each to resemble eggs.
In small resealable food-storage plastic bag, place remaining 1/2 cup frosting; seal bag. Cut small hole in one bottom corner of bag; pipe frosting around chocolate pieces to create ridge on each cupcake.
Carefully spoon chocolate decors onto frosting ridge and around chocolate pieces to resemble nest.