Creamy Shells with Tuna and Spinach
This update to the old-fashioned tuna casserole is just as delicious as you remember: It gets a fresh taste from spinach and a fun shape from shells.
- 3 tablespoons extra-virgin olive oil
- 1 small yellow onion, diced small
- 1/4 cup all-purpose flour (spooned and leveled)
- 4 cups whole milk
- Coarse salt and ground pepper
- 1 hamburger bun, torn into large pieces
- 1/4 cup grated Parmesan
- 1/2 teaspoon Italian seasoning
- 1/2 teaspoon red-pepper flakes
- 1 package (10 ounces) frozen chopped spinach, thawed and excess liquid squeezed out
- 2 cans (6 ounces each) light tuna in water, drained and flaked
- 6 ounces jumbo pasta shells (about 20), cooked according to package instructions
In a large bowl, whisk together 1 tablespoon each red-wine vinegar and extra-virgin olive oil, 1/2 teaspoon sugar, and 1/4 teaspoon Italian seasoning. Season with coarse salt and ground pepper. Add 3/4 head iceberg lettuce, chopped, and 1 tomato, cut into wedges. Toss to combine.
Preheat oven to 375 degrees. In a medium pot, heat oil over medium-high. Add onion and cook until softened, about 6 minutes. Add flour and cook, stirring constantly, 1 minute. Gradually add milk, whisking constantly, and cook until slightly thickened and bubbling, about 3 minutes. Season with salt and pepper and let sauce cool slightly.
In a food processor, combine bun, Parmesan, Italian seasoning, and red-pepper flakes. Process until fine crumbs form. Transfer half the mixture to a large bowl and combine with spinach, tuna, and half the sauce; season with salt and pepper. Fill each shell with 2 heaping tablespoons spinach mixture and place in a 9-by-13-inch baking dish. Top with remaining sauce and breadcrumb mixture. Bake until sauce is bubbling and breadcrumbs are golden, about 20 minutes.