Prepare the slow cooker: Lightly grease the inside of a 4- to 6-quart slow cooker with a little olive oil or nonstick spray to help keep the pasta from sticking.
Layer the vegetables (except spinach): Add the chopped onion, broccoli florets, sliced carrots, sliced bell peppers, frozen peas, and cherry tomatoes to the bottom of the slow cooker. Drizzle with the olive oil or melted butter and sprinkle in the garlic, Italian seasoning, dried basil (if using), salt, black pepper, and red pepper flakes.
Add the pasta: Pour the uncooked pasta evenly over the vegetables, but do not stir yet. Keeping the pasta on top helps it cook more evenly and prevents it from getting too mushy.
Mix the liquid and cheese: In a medium bowl, whisk together the vegetable broth and heavy cream or half-and-half. Stir in 3/4 cup of the grated Parmesan cheese until it’s mostly dissolved. This will form the base of your creamy sauce.
Pour in the sauce: Gently pour the broth and cream mixture over the pasta and vegetables in the slow cooker, making sure the pasta is just barely covered. If needed, press the pasta down lightly with the back of a spoon so it’s mostly submerged, but avoid stirring everything together at this stage.
Cook on low: Cover the slow cooker and cook on LOW for 2 1/2 to 3 hours, until the pasta is just tender. Every slow cooker has its own personality, so begin checking around the 2-hour mark. Give the mixture a gentle stir when you check it to help the pasta cook evenly.
Add the fresh spinach: Once the pasta is tender, add the fresh spinach by the handful, gently folding it into the hot pasta and sauce. The spinach will wilt quickly from the residual heat. If the mixture seems a bit dry, stir in an extra splash of broth or cream to loosen it.
Adjust seasoning and finish: Taste the pasta and add more salt and pepper if needed. Sprinkle the remaining 1/4 cup Parmesan cheese over the top, cover, and let it sit on WARM or LOW for another 5–10 minutes to meld the flavors.
Serve: Spoon the Spinach Pasta Primavera into warm bowls. Garnish with chopped parsley or a few extra torn spinach leaves if you like, and pass extra Parmesan at the table. Serve right away for the best texture.
Variations & Tips
This recipe is forgiving, much like the old farmhouse suppers many of us grew up with. If your crisper drawer looks a little different, feel free to swap in what you have: zucchini, yellow squash, or green beans all tuck in nicely alongside the spinach. For added protein, stir in cooked, diced chicken, sliced smoked sausage, or a can of drained white beans during the last 20–30 minutes of cooking. If you prefer a lighter dish, use all broth and skip the cream, then stir in just a splash of milk or a spoonful of cream cheese at the end for silkiness. Whole-wheat or high-fiber pasta works well but may need a touch more liquid and a few extra minutes in the slow cooker—just keep an eye on it so it stays tender, not mushy. You can also brighten the flavors with a squeeze of lemon juice right before serving, which gives a nice contrast to the creamy sauce. For those who like a bit of a crusty, baked feel, transfer the finished pasta to a casserole dish, sprinkle with extra Parmesan and a few buttered breadcrumbs, and slip it under the broiler for a minute or two. As with most good Midwestern dishes, this one reheats kindly—add a splash of broth or milk when warming leftovers on the stove to bring it back to its original, cozy creaminess.
