Begin by cooking your pasta according to the package directions. I like mine al dente. Strain the water from the cooked pasta and set the pasta aside.
Preheat your oven to 350 degrees F.
In a medium or large oven-safe Dutch oven, add a thin layer of olive oil (or bacon grease). Then add your onions and sauté they until they start to golden. Ttoss in your garlic and cook for another minute.
Next, melt your butter with the onion and garlic. When melted, slowly whisk in the flour. Continue cooking and whisking for a minute.
Slowly mix the milk into the mixture until smooth. Continue to cook the mixture while stirring frequently until it bubbles and thickens. At this point, reduce the heat to low.
Stir in the onion powder, salt, pepper, nutmeg, and pumpkin puree until smooth. Then add your shredded cheese. (I like to reserve a handful of cheese to top off the dish.) Whisk the cheese cause until melted and smooth.
Remove from heat, add your cooked pasta, and stir. Then, add your bacon and stir.
Sprinkle the panko crumbs over top. Then top with the reserved (or extra) cheese.
Cover with a lid and bake for about 20 minutes until the cheese is melted and bubbling.