1-First Step: Cook the pasta Cook 8 ounces medium pasta shells in a large pot of boiling salted water according to package instructions; drain well. Aim for al dente to avoid mushy texture in your one-pan creamy beef and shells skillet recipe. For gluten-free, use certified gluten-free shells and undercook by 1 minute. Set aside.

2-Second Step: Brown the beef Heat 1 tablespoon olive oil in a skillet over medium-high heat. Add 1 pound ground beef and cook until browned, about 3 to 5 minutes, breaking it up as it cooks; drain excess fat and set beef aside. This builds flavor fond. For low-fat, use turkey and add a splash of stock to prevent sticking. Vegan swap: lentils, simmered until firm.

3-Third Step: Saute aromatics Add ½ medium sweet onion, diced, to the skillet and cook until translucent, about 2 to 3 minutes. Stir in 2 cloves garlic, minced, and 1½ teaspoons Italian seasoning and cook about 1 minute. These layers make your cheesy tomato beef shells pop. Adjust for vegan with extra herbs.

4-Fourth Step: Build the sauce base Stir in 2 tablespoons all-purpose flour and cook until lightly browned, about 1 minute. Gradually whisk in 2 cups beef stock and 1 (15-ounce) can tomato sauce. Bring to a boil, then reduce heat and simmer, stirring occasionally, until the sauce thickens slightly, about 6 to 8 minutes. For gluten-free, use 2 tablespoons cornstarch slurry. This is the heart of your skillet beef and shells with cheesy tomato sauce.

5-Fifth Step: Combine everything Stir in the cooked pasta, browned beef, and ¾ cup heavy cream until heated through, about 1 to 2 minutes. Season with kosher salt and freshly ground black pepper to taste. Add heavy cream slowly to avoid curdling, as per tips. Lighter option: half-and-half thickened with roux.

6-Final Step: Melt the cheese and serve Stir in 6 ounces shredded extra-sharp cheddar cheese (about 1½ cups) until melted, about 2 minutes. Serve immediately for stovetop creamy beef shells pasta casserole. For baked beef shells casserole with melted cheese, transfer to oven-safe dish, top with extra cheese, and bake at 350°F for 10 to 15 minutes until bubbly. Dig in hot!