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

In a large bowl, mix peanut butter, granulated sugar, brown sugar, egg, vanilla extract, baking soda, and salt until smooth.

Roll dough into small balls (about 1 tablespoon each) and place them 2 inches apart on the baking sheet.

Flatten each ball with a fork to create a crisscross pattern.

Bake for 8-10 minutes, or until edges are golden brown. The cookies will still be soft but will firm up as they cool.

Let the cookies cool completely before assembling the sandwiches.

Melt chocolate chips in the microwave in 30-second intervals, stirring until smooth.

Spread melted chocolate on the bottom of one cookie.

Spread marshmallow fluff on the bottom of another cookie.

Sandwich them together, pressing gently so the marshmallow spreads evenly.

Let the sandwiches set for 10 minutes before serving.

For an extra toasted flavor, use a kitchen torch or briefly broil the marshmallow fluff for 30 seconds.

Enjoy warm for an ooey-gooey, melty bite!