Melt the butter over medium heat in a large pot. Once the butter is melted, add in the mini marshmallows and stir to coat in the melted butter.

Continue to stir until the marshmallows are completely melted.

Once the marshmallows are melted, remove them from the heat and stir in the vanilla extract.

Add the cereal to the marshmallow mixture and fold it in until completely coated.

Transfer the coated cereal mixture to the prepared baking dish, and smooth it into an even layer. Do so gently, as packing the cereal into the dish will create a very firm square. The goal is to have a gooey square, so a gentle hand is all that’s needed.

Cover the dish and let the treats set for at least 1 hour at room temperature. Storing in the fridge will make for a firmer treat, so room temperature is recommended if you like a gooey texture.

Remove the parchment paper, then slice and serve the Rice Krispie treats.

Store in an airtight container at room temperature for up to 3 days, or in the refrigerator for up to 5 days.