1. Preheat your oven to 350 F (175 C). Lightly grease and flour a 9×13-inch baking dish, or spray it thoroughly with non-stick baking spray. This prevents sticking and ensures easy removal of the cake.

2. In a large mixing bowl, combine the entire can of pumpkin puree and the box of spice cake mix. Use a sturdy spoon or a rubber spatula to mix these two ingredients together. It will be a thick batter, so mix until just combined and no dry streaks of cake mix remain. Avoid overmixing.

3. Gently fold in the semi-sweet chocolate chips into the batter. Distribute them evenly throughout the mixture.

4. Pour the thick batter into your prepared 9×13-inch baking dish. Use your spatula to spread the batter evenly across the bottom of the dish. It might be a bit sticky, so take your time to ensure an even layer.

5. Place the baking dish in the preheated oven and bake for 25-30 minutes. The cake is done when a wooden skewer or toothpick inserted into the center comes out clean or with moist crumbs attached, but no wet batter. The top should be lightly golden brown and spring back slightly when gently pressed.

6. Once baked, remove the cake from the oven and place it on a wire rack to cool. Allow it to cool for at least 15-20 minutes before slicing and serving. This helps the cake set and makes for cleaner slices.