Slowly melt the butter in a large pan, low heat.

Once butter is melted, add vanilla and 6 cups of marshmallows. Melt the marshmallows slowly.

Right before the marshmallows are fully melted, add milk and the other 2 cups of marshmallows. Stir until the added marshmallows are starting to melt. (we don't want them fully melt so you will have a lumpy fluff)

Add the Rice Krispie Cereal. Stir until the cereal is fully coated with the marshmallow fluff.

Dump into an 8 x 11 greased dish. Use a greased spatula to spread out the treats and press down just a bit (you don't want them to so compacted that they become rock hard).

Sprinkle the mini chocolate chips on top of the treats and press down gently to make them stay on.

Allow to fully cool before cutting and serving.