Not many kids (or adults) could resist these treats made with the classic combo of peanut butter and jelly.
Preheat oven to 375 degrees. Brush a 9-inch square baking pan with butter and line with parchment paper, leaving a 2-inch overhang on two sides. Butter parchment.
In a large bowl, whisk together flour, sugar, and salt. With a pastry cutter or your hands, work in butter until mixture resembles coarse meal with a few pea-size pieces of butter remaining. Add egg and vanilla extract; stir until dough just comes together. Set aside 1 cup dough and firmly press remaining dough into pan in an even layer. Using a small offset spatula, spread grape jelly over top.
Combine reserved dough, peanuts, and peanut butter chips; crumble over jam layer. Bake until topping is deep golden brown, 45 to 50 minutes. Let cool completely in pan on a wire rack. Run a sharp knife around edges, then, using parchment, lift cake from pan and cut into 12 squares.
Store in an airtight container, up to 1 week.