Gather all your ingredients to make the process smoother.

Melt the unsalted butter in a large saucepan over low heat. Add mini marshmallows and stir until melted and smooth.

Remove from heat and mix in peanut butter, vanilla extract, and salt. Gradually fold in crispy rice cereal until evenly coated.

Lightly grease a 9x13-inch baking dish. Pour the mixture into the dish and press down evenly with a spatula or damp hands.

Allow to cool at room temperature for 30 minutes before cutting into squares.