8 slices meaty bacon (optional)
4 tbsp. butter
1 large shallot, finely chopped
3 cloves garlic, finely chopped
Salt and pepper
3 tbsp. flour
¼ cup dry sherry or white wine
3 cups whole milk
2 jalapeño chiles, seeded and finely chopped
1 Fresno chile, seeded and finely chopped
3 oz. (6 tbsp.) cream cheese (I like Philadelphia), cut into pieces
1 lb. cavatappi (corkscrew pasta with lines) or macaroni with lines
2 cups shredded white sharp cheddar
2 cups shredded pepper Jack or Monterey Jack
1 lb. lump crabmeat or 1 lb. king crab meat (pulled from 2 lb. of legs), picked over for shells and cartilage
1 cup grated Parmigiano-Reggiano
1 cup panko breadcrumbs
3 tbsp. butter, melted
1 tbsp. Old Bay Seasoning
¼ cup finely chopped fresh chives
¼ cup chopped fresh flat-leaf parsley or cilantro leaves
Pickled mild or hot jalapeño slices
Position a rack in the center of the oven; preheat to 400°.
If using the bacon, arrange it in a single layer on a slotted broiler pan or on a wire rack set inside a baking sheet lined with foil. Bake until very crisp, 15 to 18 minutes. Let cool, then chop. Increase the oven temperature to 450°.
In a deep ovenproof skillet, melt 4 tbsp. butter over medium-high heat. Add the shallot and garlic; season with salt and pepper. Cook, stirring often, until softened, 1 to 2 minutes. Whisk in the flour. Whisk until bubbly, 30 to 60 seconds. Whisk in the sherry, then gradually whisk in the milk. Cook until the sauce is thick enough to lightly coat the back of a spoon, 3 to 5 minutes. Whisk in 3 cups water. Add the chiles and bring the sauce to a boil. Add the cream cheese and whisk until melted. Stir in the pasta. Reduce heat to a simmer and cook, stirring often, until the pasta is al dente, about 8 minutes. Stir in the cheeses a few handfuls at a time, stirring between batches to melt the cheeses. Fold in the crabmeat.
While the pasta cooks, mix the Parm, panko, melted butter, and Old Bay in a medium bowl.
Sprinkle the panko evenly over the pasta. Bake the casserole until browned in spots, 3 to 4 minutes. Top with the herbs, pickled jalapeños, and bacon (if using).