Prepare Pan:

Line your baking dish with parchment paper or lightly grease it to prevent sticking. Set aside.

Brown the Butter:

In a medium saucepan over medium heat, melt the butter. Once melted, continue cooking, swirling the pan occasionally, until the butter turns golden brown and develops a nutty aroma, about 3-5 minutes. Watch it closely to avoid burning.

Add Marshmallows:

Reduce the heat to low and add the marshmallows. Stir continuously until the marshmallows are fully melted and combined with the browned butter. Add vanilla extract and salt, if using, and mix well.

Combine with Cereal:

Remove the pan from heat and quickly stir in the Rice Krispies cereal, folding until all cereal is coated in the marshmallow mixture.

Press into Pan:

Pour the mixture into the prepared baking dish. Use a spatula or clean hands (lightly greased) to gently press down and even out the top without compressing it too tightly.

Cool and Cut:

Let the treats cool in the pan for about 20-30 minutes. Once set, lift out using the parchment paper and cut into squares.