Easiest 'make ahead' dessert I've ever come across is a "Three Milk's Cake" and guests will go for seconds while thinking you spent hours.
Basically, you bake any yellow cake in a large oblong pan (I use a cake mix). Allow cake to cool...do not remove from pan. In a large measuring cup or medium bowl with spout, mix 1 can evaporated milk, 1 can condensed milk and an equal amount of regular milk. Add teaspoon of vanilla and a 1/4 cup of spiced rum (rum is optional) and blend thoroughly. Skewer holes all over the cake and soak with milk mixture.
Cover and refrigerate anywhere from 4 to 24 hours (cake will soak up all the milk). Frost cold cake with Divinity Icing and sprinkle with cinnamon, chopped nuts, berries or whatever you fancy. I prefer yummy Divinity Icing but if frosting is not an option, serve with fresh strawberries and whipped cream.
Divinity Icing
Mix 1 cup sugar and 1/2 cup water and bring to boil (must reach 250 degrees F or medium ball stage). Set aside
Beat 2 or 3 egg whites until fluffy
Continue beating while drizzling the hot syrup into the egg whites
Add: 1/4 tsp. Cream of Tartar and 1 tsp. Vanilla