Mix the graham cracker crumbs with melted butter until the crumbs are evenly coated and resemble wet sand. Press this mixture firmly into the bottom of your tart pan, creating an even crust. Bake for 12-15 minutes until golden and fragrant, then let it cool.
Break the dark chocolate into small pieces and melt with the heavy cream in a microwave-safe bowl, microwaving in 30-second bursts and stirring until smooth and glossy. Pour the melted chocolate over the cooled crust, spreading it evenly with a spatula, and let it set for about 10 minutes in the fridge.
Warm the peanut butter in the microwave for about 20 seconds until it becomes gooey and easy to spread. Carefully spread the softened peanut butter over the set chocolate layer, smoothing it out with the back of a spoon or spatula.
Place the tart in the fridge and chill for at least 2 hours, or until the peanut butter layer is firm and the flavors have melded beautifully. This helps the layers stay together when sliced.
Once chilled, use a warm knife to slice the tart cleanly. Optionally, sprinkle chopped peanuts on top for added crunch and presentation. Serve slightly chilled or at room temperature for the most satisfying experience.