Line a 9-inch x 5-inch loaf pan with parchment paper and set it aside. (Tip: Spray the pan lightly with oil to help the parchment paper stay in place.)
In a medium bowl, stir together all of the chocolate crust ingredients until the dough sticks together. Press the dough evenly into the bottom of the lined loaf pan, and place it in the freezer to set.
To prepare the filling, stir together the peanut butter, maple syrup, coconut oil, and salt. Remove the crust from the freezer, and add the peanut butter filling on top. Smooth with a spatula, then return the pan to the fridge.
To make the chocolate topping, combine the cocoa powder, melted coconut oil, and maple syrup, whisking well to break up any clumps. (Make sure the maple syrup is at room temperature, so the topping doesn't thicken up.) Once the mixture has become a smooth chocolate sauce, pour it over the peanut butter layer, smooth the top with a spatula, and return the pan to the freezer to set until firm, about 1 hour.
To serve, remove the pan from the freezer and grab the edges of parchment paper to easily lift the solid bar from the pan. Use a sharp knife to slice the bars into small pieces. (I usually get about 20-22 pieces.)
These bars will melt if they sit at room temperature for too long, so be sure to serve them chilled. I like to transfer them to the fridge, so they aren't too hard to bite into. (They also have more flavor when served from the fridge, instead of the freezer.) You can store these in an airtight container for up to 2 weeks in the fridge, or up to 3 months in the freezer.
If you don't care for coconut oil, a vegan butter substitute that is solid at room temperature will most likely work. If you don't need a dairy-free & vegan recipe, you can also use real butter instead of the oil.