Step 1

Line an 8×8-inch baking pan with a parchment paper sling, leaving several inches of overhang on 2 sides. Melt 6 tablespoons unsalted butter in a large saucepan over medium-low heat. Reserve 1 cup from 1 (10-ounce) package mini marshmallows. Stir the remaining marshmallows (about 3 cups), 1/2 teaspoon vanilla extract, and 1/4 teaspoon kosher salt into the butter until melted. Turn off the heat.

Step 2

Add the reserved 1 cup mini marshmallows, 4 cups rice crisp cereal (such as Rice Krispies), 2 cups coarsely crushed graham crackers, and 1/2 cup milk chocolate chips, and gently fold until completely coated. Transfer mixture to prepared pan and press into an even layer. Cool 1 hour before cutting into 16 squares.