Preheat oven to 350°. Line a 9x9” baking pan with foil and spray with cooking spray. Set aside.
Mix the peanut butter, sugar, and 1 egg in a large bowl by hand. Spread into the bottom of the prepared pan. Bake for 12 minutes. While the crust is baking, make the filling.
In a medium bowl, stir together the melted and cooled chocolate with the sweetened condensed milk. Add remaining egg and vanilla and stir until combined. When crust comes out of the oven, spread chocolate mixture over hot crust. Sprinkle the peanuts evenly on top. Return to oven and bake an additional 20-25 minutes until the top bounces back when you touch it. Cool completely and cut into bars.