Devils Food Cupcakes with Coconut Pecan Frosting

1/2 cup boiling water

1/4 cup unsweetened cocoa powder (not Dutch-process)

1/4 cup whole milk

1 teaspoon vanilla extract

1 cup all-purpose flour

1/2 teaspoon baking soda

1/4 teaspoon salt

1 stick unsalted butter, softened

1/2 cup granulated sugar

1/2 cup packed dark brown sugar

2 large eggs

FOR THE FROSTING:

1/2 cup flaked sweetened coconut

1/2 cup chopped pecans

1/2 stick unsalted butter, softened

1 (8-ounce) package cream cheese, softened

1/2 teaspoon vanilla extract

3/4 cup confectioners sugar

Equipment: twelve (1/3- to 1/2-cup) muffin cups; 12 paper muffin cup liners