Heat the oven to 425°F. Bring a large pot of salted water to a boil and cook the pasta until just shy of al dente. Reserve 1/2 cup pasta water, then drain.

While the pasta cooks, pat the shrimp dry and season with a little salt and pepper.

Warm 1 tablespoon olive oil and 1 tablespoon butter in a large oven-safe skillet over medium-high heat. Add the shrimp in a single layer and cook just until pink on the first side, about 1 minute. Flip and cook 30 seconds more, then transfer to a plate.

Lower the heat to medium. Add the remaining 1 tablespoon butter, shallot, and garlic. Cook until fragrant and softened, about 1 minute. Stir in red pepper flakes.

Pour in the wine or broth and simmer for 1 to 2 minutes, scraping up any browned bits. Add the cream and simmer gently for 2 minutes.

Stir in the Parmesan, spinach, lemon zest, and lemon juice. Add the drained pasta and toss until coated. If the sauce looks tight, add a splash of reserved pasta water.

Return the shrimp to the skillet and fold everything together. Taste and adjust with salt and pepper.

Top with mozzarella or fontina, breadcrumbs, and a small drizzle of olive oil. Transfer the skillet to the oven and bake until bubbling and lightly browned on top, 6 to 8 minutes.

Let the skillet rest for a few minutes so the sauce settles, then finish with parsley and serve warm.