Soak dates in hot water to cover in a medium bowl for 10 minutes. Drain, reserving the soaking water.
Meanwhile, line an 8-inch square baking pan with parchment paper, leaving extra hanging over 2 sides. Lightly coat the parchment with cooking spray.
Combine the soaked dates, peanut butter, oats and salt in a food processor; process until very finely chopped and starting to clump together. If the mixture seems dry, add a little of the reserved soaking water, 1 tablespoon at a time. Transfer to the medium bowl and stir in peanuts. Spread the mixture evenly and firmly into the prepared pan.
Place the chocolate in a microwave-safe bowl and microwave on Medium until melted, 2 to 3 minutes. Spread the chocolate evenly over the oat mixture. Refrigerate until cold, about 1 hour. Remove from the pan by lifting the overhanging parchment. Cut into 16 squares.