Peanut Butter Cookies

Ingredients:
1/2 cup unsalted butter, softened
1 1/2 cups smooth peanut butter (not "natural")
1 cup packed dark brown sugar
1 large egg
1 3/4 cups all-purpose flour
1 teaspoon baking powder
1/2 teaspoon salt

Instructions:
1. Preheat oven to 350°F.
2. Beat together butter, peanut butter, and sugar with an electric mixer until pale and fluffy, 2 to 3 minutes.
3. Beat in egg, then remaining ingredients until a dough forms.
4. Arrange level tablespoons of dough 1 1/2 inches apart on 2 buttered baking sheets, then flatten in a crosshatch pattern to a 2 1/2-inch round with fork tines.
5. Bake in middle of oven until slightly puffed, 12 to 15 minutes. Cool on sheets 1 minute, then transfer cookies to a rack to cool completely.