Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a saucepan, melt 1/2 cup of salted butter over medium heat and cook until golden brown.

Combine the browned butter with 1/2 cup brown sugar and 1/2 cup granulated sugar until smooth.

Add 1 large egg and 1 teaspoon vanilla to the mixture, and mix until creamy.

Gradually add 1/2 teaspoon baking soda, a pinch of salt, and 1 1/2 cups all-purpose flour, mixing until just combined.

Fold in 3 cups Rice Krispie cereal and 1 cup mini marshmallows.

Scoop large balls of dough onto the prepared baking sheet, spaced 4-5 inches apart.

Bake for 10-13 minutes until edges are light golden brown and centers are slightly soft.

Sprinkle with flaked salt and allow to cool before transferring to a wire rack.