Preheat the oven to 350° F (180° C.) In a medium bowl, mix together the 1-to-1 replacement flour, baking soda, and chocolate chunks.
In a large bowl, add the peanut butter, sugar, and brown sugar, and use an electric mixer to mix at medium speed until fully combined. Next, mix in the eggs and vanilla. Finally, switch to a spatula and stir in the flour mixture until it is fully incorporated, but be careful not to overmix.
Pour the batter into a 9-inch cast iron skillet, or divide up into smaller skillets. Bake at 350° F (180° C) for about 30 minutes, and serve hot. The cookie can be stored at room temperature for about 2-3 days, or in the refrigerator for 3-4 days.