Preheat and Prep: Set your oven to 350°F and line your baking sheets with parchment paper.
Cream Wet Ingredients: In a mixing bowl, beat together the softened butter, peanut butter, brown sugar, and granulated sugar until the mixture is smooth and well-combined.
Add Egg and Vanilla: Incorporate the egg and vanilla extract, mixing until they are fully blended into the creamed mixture.
Combine Dry Ingredients: Gently stir in the flour, baking powder, espresso powder, and salt. Mix only until the dry ingredients are just combined with the wet ingredients.
Fold in Walnuts: Carefully fold in the chopped walnuts.
Scoop and Bake: Drop tablespoon-sized amounts of dough onto the prepared baking sheets and lightly flatten each cookie. Bake for 10–13 minutes, or until the edges appear set and are a light golden color.
Cool: Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
