Preheat the oven to 350 degrees. Spray a 2-quart baking dish or 9x9 inch or 11x7 inch baking pan with nonstick cooking spray.
Cook the pasta: Bring a large pot of salted water to a boil and cook the noodles until al dente, according to the directions on the package. Once done cooking, drain and set aside.
Cook your bacon: Add bacon to a large skillet or pan and place over medium heat, cook bacon on both sides until crispy and golden brown. If the pan starts to smoke at any point, simply lower the heat. Once bacon is done, blot with a paper towel to absorb excess grease, then chop into bite sized pieces and set aside.
Cook the spinach: Drain the grease from the bacon pan, then place the same pan over low heat and cook your spinach: add spinach to pan and cook until spinach wilts, the spinach will absorb any of the small amount of grease remaining on the bottom of the pan. Remove from heat and transfer to the large bowl with the noodles.
Make the cheese sauce: In the same pan, add in the butter and place over medium heat. Once butter is melted, whisk in the flour until a thick paste forms and then slowly add in milk, a little bit at a time, vigorously whisking away any lumps. Bring mixture to a boil, then reduce heat to a simmer and stir every so often, until the sauce thickens up, about 2 minutes.
Once the sauce has thickened up a bit, reduce the heat to low and stir in garlic powder, the cheddar and parmesan cheese. salt and LOTS of freshly ground black pepper. Finally stir in the pumpkin puree until smooth and well combined. Remove from heat.
Add the pumpkin cheese sauce to the bowl with the pasta and spinach. Stir well to combine and coat the pasta with the sauce, then taste and season with additional salt and pepper, as necessary. Pour mixture into the prepared baking pan and evenly spread out towards the edges. Top with remaining ½ cup shredded sharp cheddar cheese, then top with the bacon pieces.
In a small bowl, mix breadcrumbs with melted butter. Sprinkle breadcrumb mixture evenly over the top of the Mac and cheese and bake for 20 minutes or until breadcrumbs are golden brown. Serves 6.