Measure milk into 1-quart measure.
Stir in sugar.
Microwave 2 minutes on HIGH, or until sugar melts.
Add butter and vanilla.
Stir until butter melts.
Stir in coconut and nuts.
Fill cake with half the frosting.
Use remainder to frost top of cake.
Place assembled cake in oven.
Microwave 30 seconds on HIGH, to glaze and fluff frosting.