Bring a large pot of generously salted water to a boil. Cook the ravioli according to the package directions until just al dente.
Before draining, reserve approximately 1/4 cup of the pasta cooking water. Carefully drain the ravioli and set aside.
Meanwhile, melt the butter in a large skillet over medium-low heat.
Add the minced garlic, chopped sun-dried tomatoes, and Italian seasoning. Cook for approximately 1 minute, stirring frequently, until fragrant. Avoid browning the garlic.
Pour in the half-and-half. Stir in the Dijon mustard and 2 tablespoons of Parmesan.
Cook over low heat for 2–3 minutes, stirring occasionally, until the Parmesan has melted and the creamy sauce begins to thicken. Add another tablespoon of Parmesan if you prefer a thicker, cheesier sauce.
Taste and season with salt and freshly ground black pepper as needed.
Gently add the cooked ravioli and chopped baby spinach to the skillet.
Simmer gently for 3–5 minutes, or until the spinach has wilted and the ravioli are warmed through. If the sauce becomes too thick, add reserved pasta water a tablespoon at a time until it reaches your preferred consistency.
Serve the Creamy Sun-dried Tomato and Spinach Ravioli immediately with additional Parmesan and fresh basil, if desired.