Step 1: Preheat your oven to 350°F (175°C) and line an 8×8 inch square baking pan with parchment paper, leaving an overhang to easily lift the pumpkin spice candy bars later.
Step 2: In a medium bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Press the mixture firmly into the bottom of the prepared pan to form the base of your pumpkin spice candy bars.
Step 3: Bake the crust for 10 minutes until slightly golden. Remove from the oven and let it cool slightly while you prepare the filling for the pumpkin spice candy bars.
Step 4: In a large bowl, whisk together the pumpkin puree, sweetened condensed milk, egg, pumpkin pie spice, and vanilla extract until smooth and well combined.
Step 5: Pour the pumpkin mixture over the pre-baked crust and spread it evenly to ensure your pumpkin spice candy bars have uniform layers.
Step 6: Bake for another 20-25 minutes, or until the pumpkin filling is set and no longer jiggles in the center. Allow the pumpkin spice candy bars to cool completely at room temperature.
Step 7: In a microwave-safe bowl, combine the chocolate chips and coconut oil. Microwave in 30-second increments, stirring in between, until the chocolate is completely melted and glossy.
Step 8: Pour the melted chocolate over the cooled pumpkin layer and spread evenly. Refrigerate the pumpkin spice candy bars for at least 3 hours, or until the chocolate is firm, before slicing into bars.