Combine graham cracker crumbs, sugar, and a pinch of salt in a mixing bowl, then pour in the melted butter. Mix until the crumbs are evenly coated and the mixture resembles wet sand.
Press the crumb mixture evenly into the bottom and up the sides of your tart pan with your fingers or a spatula. Once pressed, bake in a preheated oven at 180°C (350°F) for about 10 minutes until set and fragrant. Remove and let cool slightly.
While the crust cools, chop the dark chocolate into small pieces and melt it gently in a microwave or double boiler until smooth and glossy, about 2-3 minutes in the microwave, stirring every 30 seconds.
In a separate bowl, stir the peanut butter, powdered sugar, and a pinch of salt until smooth and creamy. Spread this evenly over the cooled crust, pressing gently to set the layer.
Pour the melted chocolate over the peanut butter layer, spreading it smoothly with a spatula. Gently tap the tart pan on the counter to settle the layers and remove any air bubbles.
Place the tart in the refrigerator and chill for at least 2 hours, or until the chocolate is firm and the layers are set. Cover loosely if needed.
Just before serving, optionally sprinkle chopped peanuts or drizzle with melted chocolate for extra decoration and crunch. Slice with a warm, sharp knife for clean cuts and enjoy the rich contrast of flavors and textures.