1-First Step: Prep the pasta and oven Start by heating your oven to 375°F. Bring a large pot of water to a boil and salt it well so the spaghetti has flavor from the start. Cook the dried spaghetti noodles until just shy of al dente, since they will finish cooking in the oven. Drain the pasta and set it aside. If you are cooking for a crowd, this is a great place to line up your baking dish, cheese, and chopped parsley so the rest of the process feels smooth. A little prep now saves time later, especially on weeknights.

2-Second Step: Brown the sausage and soften the vegetables Set a large skillet over medium heat and melt the butter. Add the Italian sausage and cook it until browned, breaking it into small pieces as it cooks. Once the sausage is mostly cooked through, add the diced onion and keep stirring until it softens. Next, stir in the sun-dried tomatoes and minced garlic. Cook for about 1 minute, just until fragrant. This is where Tuscan baked spaghetti starts to smell amazing, with that rich mix of sausage, garlic, and tomato working together.

3-Third Step: Build the creamy sauce Sprinkle the flour over the sausage mixture and stir it in so the fat is coated. Cook for about 1 minute to take away the raw flour taste. Slowly pour in the milk while whisking or stirring constantly. This helps the sauce stay smooth instead of clumpy. Add the kosher salt, Italian seasoning, and black pepper. Keep stirring as the sauce thickens, which usually takes a few minutes. Once it starts to look silky and lightly thickened, you are ready for the greens.

4-Fourth Step: Add the spinach and pasta Add the baby spinach to the skillet in handfuls, stirring until it wilts into the sauce. This only takes a couple of minutes. Then fold in the cooked spaghetti until every strand is coated with the creamy sausage mixture. Try not to overmix once the pasta goes in. Gentle folding helps keep the noodles intact and gives you a prettier baked pasta at the end. If the mixture looks a little thick, a splash of the reserved pasta water can loosen it.

5-Fifth Step: Transfer to the baking dish Grease a 9 by 13 inch baking dish, then spoon in the spaghetti mixture. Spread it out evenly so the top bakes in a nice, even layer. Sprinkle the shredded mozzarella over the top for that golden, melty finish everyone expects from a baked spaghetti recipe. If you like a little extra cheese, you can add a small amount more on top, but the listed amount already gives you a good bubbly layer without overpowering the sauce.

6-Final Step: Bake and serve Bake the Tuscan baked spaghetti for about 20 to 25 minutes, or until it is hot and the cheese has melted and turned lightly golden. Let it rest for 5 to 10 minutes before serving so the sauce settles a bit and the portions hold together better. Finish with chopped parsley if you want a fresh look. Serve warm and enjoy a dinner that feels rich, homey, and very satisfying. If you are planning a full meal, it pairs nicely with a crisp salad or simple garlic bread.