Measure out 10 cups of mini marshmallows. Then set 2 cups aside for later.

Line a 9x13 inch baking dish with parchment paper. You can skip the parchment paper and grease your pan with butter if you prefer.

In a large saucepan, melt the butter and 8 cups of mini marshmallows over medium-low heat. Stir until melted. then stir in the salt and vanilla extract.

Mix in the rice krispies and additional 2 cups of marshmallows, stir until completely coated.

Add in the Christmas M&Ms and Christmas sprinkles, mixing until combined.

Transfer the mixture to the baking dish. Gently press the rice krispies into the pan. The more you press them down, they become more dense and not quite as airy and gooey. Pro tip: use slightly wet hands when pressing them, this helps to prevent the mixture from sticking to your hands.

Press additional M&Ms and sprinkles on the top if you want.

Allow them to set, about 1 hour. Then slice with a sharp knife into squares and enjoy.