In a mixing bowl, sift the flour, baking soda, and salt. Set aside. Using a mixer, beat the butter, brown sugar, and sugar on high. Beat until light and fluffy. Add in the peanut butter and mix until combined. Add in the vanilla and egg. Mix until combined. Scrape the bowl and mix for 10 seconds.
1 ¼ cup All-purpose flour, ½ teaspoon Baking soda, ½ teaspoon Salt, ½ cup Unsalted butter, ⅔ cup Brown sugar, ⅓ cup White granulated sugar, ½ cup Peanut butter, 1 Large egg, 1 teaspoon Pure vanilla extract