Put the bowl back in the microwave and heat in 40 second increment, whisking after each time, until the marshmallows are melted and the marshmallows and butter are fully incorporated.
Pour the cocoa pebbles and mini marshmallows into the melted marshmallows. Use a spatula to combine and coat completely. Press the treats into a greased 9 x 13 pan and set aside.
Heat chocolate chips with unsalted butter or vegan baking stick in the microwave. Once melted, stir in the cocoa pebbles. Spread the mixture on top of the cocoa pebble treats.
Melt more chocolate chips. Pour over the chocolate crunch topping for a smooth finish and place down some extra mini marshmallows into the melted chocolate so they stick.