Necco Sweethearts Cupcakes

Chocolate Cupcakes
1 cup semisweet-chocolate chips
1/3 cup milk
2 cups all-purpose flour
1 cup unsweetened cocoa powder
2 teaspoons baking soda
1/4 teaspoon salt
2 cups granulated sugar
1 cup mayonnaise
4 large eggs
1 teaspoon vanilla extract
3/4 cup water

Vanilla Frosting
1/2 cup unsalted butter, softened
3 cups confectioners