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Sourdough Peanut Butter Sandwich Cookies (Soft & Chewy)

These soft and chewy sourdough peanut butter sandwich cookies are filled with a sweet peanut butter buttercream — the perfect from-scratch treat using sourdough discard.

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Ingredients

For the Cookies:

  • ½ cup unsalted butter, softened
  • ½ cup creamy peanut butter (not natural/separated)
  • ½ cup brown sugar
  • ¼ cup graulated sugar
  • ½ cup sourdough discard (unfed, room temp)
  • 1 egg
  • 1 tsp vanilla extract
  • 1⅓ cup all-purpose flour
  • ½ tsp baking soda
  • ½ tsp baking powder
  • ½ tsp salt

Peanut Butter Filling

  • ½ cup creamy peanut butter
  • ¼ cup unsalted butter, softened
  • 1⅓ cup powdered sugar
  • 1-2 tbsp heavy cream or milk
  • ½ tsp vanilla extract
  • pinch of salt

Instructions

Make the Cookie Dough

  • In a mixing bowl, cream the butter, peanut butter, brown sugar, and granulated sugar until light and fluffy.
  • Mix in sourdough discard, egg, and vanilla.
  • In a separate bowl, whisk together flour, baking soda, baking powder, and salt.
  • Add dry ingredients to wet and mix just until combined. Cover and chill 30 minutes (optional but helps shape + softness).

Shape & Bake

  • Preheat oven to 350°F and line a baking sheet with parchment paper.
  • Scoop 1 to 1½ tablespoon–size balls of dough and lightly flatten with a fork (classic criss-cross optional).
  • Bake 8–9 minutes — just until set but still soft in the center.
  • Let cool completely before filling.

Make the Filling

  • Beat peanut butter and butter until smooth.
  • Slowly add powdered sugar, then cream and vanilla.
  • Whip until fluffy and pipeable. Add a pinch of salt if desired.

Assemble the Sandwich Cookies

  • Pair cookies by size.
  • Pipe or spread filling onto the flat side of one cookie, top with another.
  • Chill 5–10 minutes for the BEST texture.