Preheat oven to 350°F and line a muffin pan for 14 cupcakes.
Whisk together flour, cornstarch, baking powder, baking soda, and salt.
Beat butter and sugar until light and fluffy.
Mix in egg whites, vanilla extract, and almond extract if using.
Alternate adding dry ingredients and milk, mixing just until combined.
Fold in sour cream gently without overmixing.
Fill cupcake liners two-thirds full.
Bake 18 to 22 minutes or until a toothpick inserted in the center comes out clean.
Cool cupcakes completely.
Beat butter for frosting until creamy.
Gradually add powdered sugar.
Mix in heavy cream, vanilla extract, coconut extract if using, and salt.
Add blue gel food coloring until you reach a pale robin’s egg shade.
Frost completely cooled cupcakes.
Mix cocoa powder with vanilla extract until thin.
Flick mixture lightly over frosted cupcakes to create speckles.
Top each cupcake with three mini chocolate eggs.