In a large mixing bowl, cream together unsalted butter, creamy peanut butter, granulated sugar, and brown sugar until smooth. Beat in egg and vanilla extract.

Stir in all-purpose flour, baking soda, and salt until just combined.

Gently fold in mini marshmallows and peanut butter chips until evenly distributed.

Cover the dough and chill in the refrigerator for 30 minutes.

Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper. Scoop the dough into 1.5-tablespoon sized balls (about 18 cookies total) and place on the sheet 2 inches apart.

Bake for 10-12 minutes or until edges are golden but centers look slightly underbaked. Let them rest on the sheet for 5 minutes before transferring to a wire rack.