Preheat the oven to 350°F (180°C). Butter and line the pan with parchment paper, leaving an overhang on two sides. That way, it will be easier to lift the blondie after baking.
Melt the butter in a saucepan over low heat or in the microwave at 20-second intervals. In a bowl, mix the two sugars with the melted butter and vanilla extract. Use a hand whisk.
Add the peanut butter at room temperature and mix just until combined.
Mix in the eggs until smooth.
Add the flour, baking powder, and salt and mix with a spatula until combined.
Reserve two tablespoons each of chopped peanuts and white chocolate chips. Add the rest of the chopped peanuts and chocolate chips to the batter and mix.
Pour the batter over the mold and spread even with the spatula. Add the extra peanuts and chocolate chips as a topping before baking.
Bake in a preheated oven at 360°F for 30-35 minutes. You can tell when it’s done when poking it with a knife it comes out clean or with a few crumbs.
Let cool for at least 15-20 minutes before decorating. To decorate, heat the peanut butter for about 20 seconds in the microwave and when it is very soft, let it fall on the blondie in the form of ribbons. Sprinkle chopped white chocolate chips.
To unmold, cool completely, and pull the parchment paper firmly from the edges. It will come out of the pan easily. Cut once unmolded.