How to Make It
Preheat oven to 350°F with oven rack in lower third of oven. Unfold 1 puff pastry sheet on a lightly floured sheet of parchment paper; roll into a 10-inch square. (Trim and discard excess pastry, if necessary.) Spread 1½ tablespoons of the peanut butter down the center of the square. Top peanut butter evenly with 2 tablespoons of the preserves. Cut slits crosswise 1 inch apart on both sides of filling to within ½ inch of filling. Starting at 1 end, fold pastry strips over filling, alternating left and right, to cover filling in a braid design. Pinch ends of braid to seal, and fold under to enclose filling. Place braid on a parchment paper-lined baking sheet. Repeat process with second puff pastry sheet and remaining 1½ tablespoons peanut butter and 2 tablespoons preserves.
Whisk together egg yolk and water in a small bowl; brush dough evenly with egg mixture. Sprinkle tops of braids evenly with peanuts. Bake in preheated oven until golden brown, 30 to 33 minutes, rotating pan on rack after 15 minutes.
Let braids stand on baking sheet 5 minutes. Transfer to a serving plate. Serve slices of pastry braids warm or at room temperature.