Preheat your oven to 180°C (350°F). In a mixing bowl, combine the graham cracker crumbs, melted butter, and salt until well mixed and the mixture holds together when pressed.
Press the crumb mixture evenly into the bottom and up the sides of your tart pan. Use the back of a spoon or your fingers to smooth the surface. Bake for 10-12 minutes until the crust is golden and fragrant.
While the crust bakes, melt the chopped dark chocolate with the heavy cream in a saucepan over low heat. Stir gently until the mixture is smooth, glossy, and fully combined.
Remove the saucepan from heat and stir in the peanut butter until the ganache is silky and uniform in color. Let it cool slightly to thicken but remain pourable.
Pour the warm ganache into the pre-baked crust, smoothing the top with a spatula. Place the tart in the refrigerator and chill for at least 4 hours, or preferably overnight, until the filling is firm and shiny.
Once set, remove the tart from the fridge. Slice into wedges and serve, optionally garnished with chopped peanuts or chocolate shavings for extra texture and presentation.