Best Darn Pumpkin Mac and Cheese

Preheat the oven to 375 degrees (F). Lightly grease a 3-quart baking dish and set aside until needed. 
Bring a large pot of water to a boil over high heat. Add the salt and pasta and cook for 4 minutes. The pasta will be very al dente. Pour pasta into a prepared baking dish and set aside until needed.
In a large skillet over medium-heat, cook the bacon until crispy on both sides, about 4 to 5 minutes per side. Remove from heat and place on a paper towel-lined plate. Blot any excess oil with a paper towel, then chop into small bits. Set aside. 
In a large pan, melt the butter over medium-heat. Add in the chopped shallots and cook, stirring frequently, for 5 to 6 minutes, or until softened and nearly translucent. Stir in the sage and garlic and cook for 1 to 2 more minutes, or until fragrant. 
Sprinkle in the flour, and stirring constantly, cook for 1 minute. Slowly pour in the milk, whisking constantly as you add. Whisk in the pumpkin puree until smooth.
Cook, whisking constantly, until the mixture begins to thicken, about 5 minutes. Whisk in the dijon mustard, brown sugar, salt, cayenne pepper, onion powder, black pepper, and nutmeg.  
Reduce to low heat. Whisk in the heavy cream, then fold in the cheeses and 1/2 of the chopped bacon.
Remove from heat and immediately pour the sauce over cooked pasta and stir gently to combine. 
In a small bowl combine the bread crumbs and olive oil, mixing well until the bread crumbs are evenly coated in the oil. Sprinkle evenly on top of the macaroni and cheese. 
Place the baking dish in the preheated oven, cover with foil, and bake for 12 minutes. Remove from the oven, sprinkle the top with remaining bacon, and bake uncovered for an additional 5 minutes. Garish with extra sage leaves, if desired. Serve warm!