Add milk and sugar in a bowl and whisk well. Stir in cream and vanilla and whisk well. Whisk in cake mix for about a minute, making sure all lumps are gone.
1 cup milk, ¾ cup sugar, 2 cup heavy whipping cream, 1 tsp vanilla extract, ⅔ cup Funfetti cake mix
Pour into a 1-1/2 quart casserole dish and top with sprinkles. Freeze for 4-6 hours or overnight until firm.