In a stand mixer or large mixing bowl, use a medium-low speed setting to mix together the vegan butter and 1 cup peanut butter.
Add graham cracker crumbs and confectioners' sugar. Continue mixing on medium-low until well blended.
Into a parchment-lined 8x11-inch pan, press the filling onto the bottom in an even layer.
Refrigerate for 30 minutes. This helps to keep the warm chocolate topping from seeping into the peanut butter layer.