Preparation

• Position a rack in the center of the oven and heat to 350°F.
• In a large bowl, stir the peanut butter and the two sugars until smooth. Add the eggs and yolk, zest, and vanilla, and beat until smooth. Add the cornstarch, salt, cayenne, and baking soda, and stir until smooth. Fold in 1/2 cup of the peanuts.
• Transfer to a heavy-duty 8-inch ovenproof skillet, smooth the top, and sprinkle with the remaining peanuts. Bake until the center looks set and the cookie is beginning to pull away from the side of the pan, 30 to 33 minutes. Let cool slightly before serving.

Mini Skillet Cookies: Use mini (3-1/2 inch) cast-iron skillets for making individual servings. Divide the batter among 8 pans, and bake on a rimmed baking sheet for easy handling. They’ll be done about 10 minutes sooner than an 8-inch cookie.