Bake a prepare cake according to the box in a 13x9 pan.

Once it comes out of the oven, use a straw to poke holes throughout the cake.

Mix the 2 boxes of instant pudding mix with 3 cups of milk until well mixed.

Pour the pudding over the cake, over the holes. Cover and refrigerate for atleast 2 hours. Top with the mini marshmallows and serve.