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

In a medium saucepan, brown the salted butter over medium heat, stirring continuously for about 5-7 minutes. Allow to cool for 10 minutes.

In a large mixing bowl, combine the cooled browned butter with brown and granulated sugars. Mix until smooth, then add the egg and vanilla, stirring until fully incorporated.

Gradually add baking soda, salt, and flour to the wet mixture, mixing gently until just combined.

Fold in the rice krispies and mini marshmallows until evenly distributed.

Scoop large balls of dough (about 3 tablespoons each) onto the baking sheet, leaving space in between.

Bake for 10-13 minutes, until edges are golden and centers remain soft.

Sprinkle with flaked salt immediately after baking and cool on the sheet for a few minutes before transferring to a wire rack.