Cook Pasta: bring a large pot of water to a boil over medium-high heat, add 1 pound medium shell noodles, and cook, al dente, according to package directions - reserve approx. 1 cup of pasta water!
Make Roux: bring a large cast iron skillet to a medium high heat, add 3 tablespoons butter, and let melt. Add 1 teaspoon garlic to the hot skillet and move around until fragrant. Whisk in 4 tablespoons all-purpose flour to create a roux. Gradually pour in the creamer, whisking continuously.
Pumpkin & Spices: Add 1 cup pumpkin pureé, 1 teaspoon dried sage, 1 teaspoon dijon mustard, 3/4 teaspoon kosher salt and 1/8 teaspoon ground black pepper - continue whisking to combine everything together. Add splashes of the reserved pasta water to thin out, as needed (we used approx. 1/4-1/2 cup here).
Make it Cheesy: Once the mixture is combined and you have reached your desired consistency, remove from heat and mix in 2 cups of cheddar cheese to melt.
Add Noodles: Add the drained noodles in the skillet with the creamy sauce and toss to coat. Add additional splashes of the reserved pasta water to reach your desired consistency and creaminess (remember the pasta will continue to soak up the liquid). Taste, add any additional salt, as desired.
Bake: Sprinkle the remaining cheddar cheese on top and then the breadcrumbs. Move the entire skillet to the oven to bake for 10 minutes or until golden brown on top.