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

In a large bowl, mix the softened butter, granulated sugar, brown sugar, egg, and vanilla until everything is smooth and creamy.

In a separate bowl, whisk together your flour, salt, and baking soda.

Gently fold the dry ingredients into the wet. When the dough is almost fully mixed, toss in about 1 cup of the marshmallows and fold until just combined.

Scoop out your dough using a medium cookie scoop and place them on your baking sheet.

Press a few of the reserved marshmallows on top of each dough ball for that pop of color.

Bake for 8–10 minutes until the edges are just golden and the centers look set.

Let them cool for 5 minutes on the pan, then transfer to a wire rack.