Preheat oven to 350F. Spray a 2 quart baking dish with oil.

Put diced king cake in the prepared dish, making sure the surface is covered. 

In a large mixing bowl, whisk together eggs, heavy whipping cream, milk, and vanilla until well combined. Pour this mixture over the diced king cake and use a spatula to gently press the king cake down so everything is covered. 

Bake for 30 minutes; cover with aluminum foil and bake another 15 - 20 minutes, or until the custard is set. 

Serve hot with vanilla ice cream on top.