*FREEZE marshmallows for at least 1-2 hours before using. Keep marshmallows in freezer until ready to bake.

Preheat oven to 350 degrees Fahrenheit. Line cookie sheets with a silicone baking mat or parchment paper. Set aside.

In a medium bowl, stir together the flour, baking soda and salt. Set aside.

Cream the butter and both sugars with an electric mixer until light and creamy.

Add the peanut butter, egg, and vanilla. Mix well and scrape bowl. Add the dry ingredients and mix until almost incorporated.

Remove marshmallows from freezer and fold a heaping cup of marshmallows into the cookie dough.

Use a #30 scoop (about 2 Tbsp) to quickly shape the cookie dough into balls. Place a few inches apart on a prepared baking sheet. Place remaining cookie dough in the fridge to keep marshmallows cold until ready to bake.

Bake cookies at 350˚F for 11-12 minutes or until just set and edges are starting to brown. Allow cookies to cool completely on tray, about 10 minutes. After 2-3 minutes of cooling, use a greased spatula to round any misshapen cookies, if desired. Transfer cooled cookies directly to serving platter or airtight container. May stick to a wire cooling rack.