Try matching pudding flavor with the cake (like butterscotch with spice cake, chocolate with chocolate cake, etc). But, red velvet cake mix and white chocolate pudding are also great together.

Chocolate cake mix - I use a 13.5 oz box mix for this recipe, not the 15 oz package Heavy cream Instant chocolate pudding mix - use the 5.9 or 6 ounce package Unsalted butter - softened at room ...