Food & Cooking Recipes Ingredients Seafood Recipes Creamy Shells with Tuna and Spinach 3.5 (205) 10 Reviews By Martha Stewart Test Kitchen Martha Stewart Test Kitchen The recipes developed by our test kitchen team have undergone a rigorous process of development and testing, ensuring that every element is optimal, from ingredient amounts to method and cooking time. This process includes triple-testing recipes to ensure they meet our high standards. The many stellar cooks and food editors who have been part of our team include Sarah Carey, Lucinda Scala Quinn, Jennifer Aaronson, Shira Bocar, Anna Kovel, Greg Lofts, Riley Wofford, Lauren Tyrell, and Lindsay Leopold. Editorial Guidelines Updated on May 16, 2017 Print Rate It Share Share Tweet Pin Email Prep Time: 30 mins Total Time: 50 mins Servings: 4 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. Ingredients 3 tablespoons extra-virgin olive oil 1 small yellow onion, diced small ¼ cup all-purpose flour (spooned and leveled) 4 cups whole milk Coarse salt and ground pepper 1 hamburger bun, torn into large pieces ¼ cup grated Parmesan ½ teaspoon Italian seasoning ½ 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 Directions 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. Cook's Notes Toss Together a Salad: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. Rate it Print