1-First step: Prep the oven and pasta water Heat your oven to 375°F. At the same time, bring a large pot of heavily salted water to a boil. Salting the water well helps the spaghetti taste better from the inside out, which is especially important in baked pasta dishes like Tuscan Baked Spaghetti. Add 1 pound dried spaghetti noodles and cook them 1 minute less than the package directions for al dente. This matters because the pasta will keep cooking in the oven later. If you cook it too long now, the final dish can turn soft or mushy.

2-Second step: Brown the sausage While the pasta cooks, melt 2 tablespoons unsalted butter in a Dutch oven over medium-high heat. Add 1 pound raw mild or spicy Italian sausage, breaking it up as it cooks. Continue until it is no longer pink, about 5 to 7 minutes. The sausage should be browned and fully cooked before you move on.

3-Third step: Build the sauce base Stir in 1 medium yellow onion, diced, about 1 1/2 cups, along with 1 cup julienne-cut sun-dried tomatoes, 3 minced garlic cloves, 1 1/2 teaspoons kosher salt, 1 teaspoon dried Italian seasoning, and 1/4 teaspoon freshly ground black pepper. Cook this mixture for about 4 minutes, or until the onion softens and the garlic smells fragrant. This is where the dish starts to taste like a true Tuscan baked spaghetti recipe. The onions bring sweetness, the sun-dried tomatoes add tang, and the garlic gives the sauce a warm savory base. Stir often so nothing sticks to the bottom of the pot.

4-Fourth step: Thicken the sauce Sprinkle 3 tablespoons all-purpose flour over the sausage mixture and stir it in well. Cook for 1 minute to remove the raw flour taste. Then slowly whisk in 4 cups whole or 2% milk, a little at a time, so the sauce stays smooth and creamy. Bring the mixture to a boil, then lower the heat and simmer until thickened, about 5 minutes. The sauce should lightly coat a spoon. If it looks too thick, add a splash more milk. If it looks too thin, simmer for another minute or two.

5-Fifth step: Add the spinach Stir in 5 ounces baby spinach, about 5 packed cups, and let it wilt into the sauce. This only takes a minute or two. The spinach adds freshness and color, and it blends right into the creamy sauce without overpowering the dish.

6-Sixth step: Combine with pasta and bake Drain the spaghetti and add it directly to the sauce. Toss everything together until the noodles are evenly coated. Transfer the mixture to a baking dish, spreading it out so the top bakes evenly. Sprinkle 3 ounces shredded low-moisture mozzarella cheese, about 3/4 cup, over the top. Bake at 375°F for 18 to 20 minutes, or until the dish is bubbling and the cheese has melted. The top should look lightly golden and inviting.

7-Final step: Rest and serve Remove the baked spaghetti from the oven and let it cool for 5 minutes. This short rest helps the sauce settle so the portions hold together better. If you want a little fresh color, finish with finely chopped fresh parsley leaves for garnish.