Prepare pan. Lightly spray x 9x13 pan or line with parchment paper (or tinfoil) for easy removal. Then spray with cooking spray. You can use a smaller pan if you want thicker treats.
Melt butter. In a large, heavy-bottomed pot, over low heat, melt butter until completely melted and smooth.
Melt marshmallows. Set aside 2 cups of the marshmallows. When butter is melted, add the remaining marshmallows. Stir with a rubber spatula or a wooden spoon until melted.
Add vanilla and salt. Remove from heat. Stir in vanilla extract and salt.
Add remaining ingredients. Immediately stir in remaining 2 cups mini marshmallows, cocoa rice krispies and chocolate chips. This can cool and set quickly so be sure to stir in immediately and then spread into your pan.
Press in pan. Spread in pan (I like to use a piece of saran wrap lightly sprayed with cooking spray, a piece of wax paper, the butter wrapper, or you can spray your hand with cooking spray) and press into the pan. Be sure to not press down too hard or it can make them very hard and compact. Let sit for 1 hour to harden. Lift out of the pan and cut into squares and enjoy.