1/2 cup butter (1 stick, 4 ounces), room temperature
1/2 cup sugar
1/2 cup packed brown sugar
1/2 cup peanut butter
1 1/4 cups all purpose flour
3/4 teaspoon baking soda
1/2 teaspoon baking powder
1/4 teaspoon salt
Beat the butter until creamy, 2 minutes. Add the sugars, beat for 2 more minutes. Mix in the peanut butter and the egg. Vigorously whisk together the dry ingredients— the flour, baking soda, baking powder and salt—in a separate bowl. Stir the dry ingredients into the sugar butter mixture.
Wrap dough in plastic and refrigerate at least 3 hours.
Preheat oven to 375°F (190°C). Shape the dough into 1 1/4 inch balls. Place the balls of dough about 3 inches apart on ungreased cookie sheet. Flatten in crisscross pattern with a fork.
Bake until light brown, about 9 to 10 minutes. Remove the cookies from the oven and let cool in their baking sheets for a minute. After a minute, transfer the cookies to a rack to cool completely.
For chewier cookies, bake at 300°F (150°C) for 15 minutes.