In a food processor, combine 4 cups of gluten-free pretzels (regular works too!), 2/3 cup smooth, unsweetened peanut butter, 1/4 cup agave or maple syrup, and 2 tablespoons melted coconut oil. Pulse until it forms a fine crumb mixture.
Pour the mixture into a 9" tart pan with a removable bottom. Use your fingers or the bottom of a round measuring cup to press the crust firmly into the pan and up the sides. Place the crust in the freezer to firm up while you prepare the chocolate filling.
In a small saucepan, heat a can of full-fat coconut milk over medium-low heat (don't let it boil). Meanwhile, chop 12 oz of dark chocolate into shards or use chocolate chips.
Place the chocolate in a heat-safe bowl and pour the hot coconut milk over it. Cover with a tea towel and let it sit for about 2 minutes. Then, stir until the chocolate is fully melted, creating a creamy ganache.
Pour the chocolate filling into the crust and refrigerate for a few hours until set. Optionally, top with chopped peanuts before serving.