For the Squash Purée: Using a vegetable peeler, remove the outer skin of the butternut squash.

Slice the squash in half lengthwise and scoop out the seeds with a spoon.

Cut into chunks smaller than 1 inch.

Toss the squash with olive oil and a generous pinch of salt.

Spread onto a baking sheet, cover tightly with foil, and roast at 375°F for 40 minutes or until extremely tender.

Transfer to a blender and blend until completely smooth.

If needed, add a splash of milk to help the mixture blend—only use as much as necessary.

Taste and adjust salt. Set aside.

For the Toppings: Add the diced pancetta to a cold pan—this ensures it renders evenly.

Place over medium-low heat and slowly render out the fat until the pancetta is crispy.

Remove the pancetta and reserve the rendered fat in the pan.

Add sage leaves to the fat and fry on medium heat until crispy.

Remove and place on paper towels to drain. Set both aside for garnish.

For the Cheese Sauce: In a large saucepot (large enough to eventually fit the pasta), melt 2–3 tbsp of butter.

Add the finely diced shallot and a pinch of salt, and cook until lightly translucent and sweated.

Add chopped fresh sage and sliced garlic. Sauté for about 1 minute, stirring often, until fragrant.

Sprinkle in the flour and whisk constantly over low heat for 2 minutes, until the raw flour smell is gone and it starts to smell nutty.

Slowly whisk in the milk a little at a time to avoid clumping.

Raise heat to medium and let it gently simmer for 5 minutes—stir frequently to prevent the bottom from burning.

Reduce heat to low, grate in fresh nutmeg (no more than ½ tsp), and taste for salt.

Start adding ⅔ of the grated fontina and cheddar cheeses by the handful, letting each addition melt before adding more.

Thin the sauce with additional milk if it becomes too thick.

Once melted and smooth, kill the heat and add the goat cheese.

If the sauce turns grainy, add 1 tbsp butter and ¼ cup milk, then blend it back smooth using an immersion blender as a fail-safe.

For the Pasta and Assembly: Boil the shellbows in salted water until al dente.

Drain, then stir the pasta directly into the cheese sauce and mix to fully coat.

Butter your baking dish (an 8” cast iron skillet works well, but only fits about half the batch).

Add a layer of mac and cheese to the bottom.

Top with a thin layer of grated cheese and a few dollops of goat cheese.

Add another layer of mac and finish with one last light layer of grated cheese on top.

Broil until golden brown and bubbly on top.

Garnish and Serve: Top with crispy pancetta and fried sage leaves.

Serve hot, straight from the skillet.