1/2 c. plus 1 tbsp. natural, chunky-style unsalted peanut butter
To prepare cookies: In a medium skillet, melt 1 stick of butter over medium heat. Using a small paring knife, split vanilla bean lengthwise. With back of knife, scrape out pulp and seeds, and add scrapings and pod to butter. Add oats and cook for 5 to 7 minutes, stirring constantly, until oats are lightly toasted and a golden-brown color. Remove and discard vanilla pod, transfer mixture to a large bowl and refrigerate.
In bowl of an electric mixer fitted with a paddle attachment, cream remaining 2 sticks butter, baking soda and salt on low speed for 2 to 3 minutes, until butter is softened. Add granulated sugar and light-brown sugar and mix on medium speed until mixture is light and fluffy, scraping down sides of bowl as needed. Add peanut butter and mix to combine. Turn mixer off and add oat mixture and flour. Turn mixer to low speed and mix another minute, until ingredients are incorporated and dough pulls away from sides of bowl and comes together in a ball.