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

Whisk together the flour, baking soda, and salt in a bowl until well combined.

Cream the softened butter, peanut butter, and both sugars together until light and fluffy, about 3-5 minutes.

Add the egg and vanilla extract, mixing until fully incorporated.

Mix in the dry ingredients until a soft dough forms, being careful not to overmix.

Shape the dough into peanut-like ovals, placing them on the prepared baking sheet.

Press crisscross marks into each cookie with a fork.

Bake for 10–12 minutes until the edges are light golden brown.

Cool the cookies completely on a wire rack before proceeding to the filling.

Beat the filling ingredients together until smooth and creamy.

Sandwich each cookie with a generous dollop of filling, gently pressing them together.