To make the cake:

Preheat oven to 350°F. Grease an 8.5- x 4.5-inch loaf pan.

Whisk together flour, cocoa, baking powder and baking soda in a small bowl. Set aside.

Place sugars and butter in a large bowl and beat until light and fluffy. Mix in eggs, one at a time, followed by milk, liqueur and vanilla. Gently stir in flour mixture and chocolate chunks until just combined. Pour cake mixture into prepared loaf pan and bake for 45-55 minutes or until toothpick inserted in loaf comes out mostly clean. Cool for 15 minutes in pan before removing to finish cooling on rack.

You may freeze the loaf at this point. Wrap tightly and store in freezer for up to 6 weeks.

To make the frosting:

Whisk together cocoa powder and powdered sugar in a small bowl. Stir together melted butter and 4 tablespoons liqueur and pour into cocoa mixture. Stir until smooth, adding remaining tablespoon of liqueur if needed. Put a cooling rack on a sheet pan and place cooled cake on rack. Pour frosting over cake.

Note: You may have extra frosting leftover depending on how much you add to your loaf cake.