heat oven to 350. Lightly spray a bundt pan w/ cooking spray. In lg bowl, Beat cake mix, pudding mix, sour cream, oil, eggs and water until smooth. Stir in almost all the chopped candy, leaving a handful for sprinkling on top of cake.
Bake about an hour. My oven it took 50 mins, but my daughters oven took an hour, so check at about 50 mins. be sure to not over bake. You want this cake moist.
Let the cake cool for just a bit. In medium saucepan, over low heat, combine peanut butter baking chips, marshmellows and evaporated milk. Stir until melted and smooth. Drizzle over still warm cake. Sprinkle top of cake w/ remaining chopped candy.