Cook the Pasta: Fill a large pot with water, season generously with salt, and bring it to a boil. Add your pasta and cook until just tender but still firm to the bite (al dente), following package instructions. Reserve about a cup of the pasta cooking water before draining.
Prepare the Roux Base: While the pasta cooks, melt butter in a large skillet over medium-high heat. Once melted, sprinkle in the flour and stir constantly for about one minute to form a light roux. This will help thicken your sauce smoothly.
Build the Sauce Flavor: Add the minced garlic to the roux and sauté briefly until fragrant, about 30 seconds. Pour in the white wine or broth, allowing it to simmer and reduce by roughly half, which should take about 1 minute. This intensifies the flavor while evaporating alcohol if using wine.
Make the Creamy Sauce: Slowly whisk in the heavy cream, Dijon mustard (if using), and Italian seasoning until the sauce is evenly combined and smooth. Let the sauce cook gently for 2-3 minutes to begin thickening.
Add Fresh Tomatoes: Stir in the chopped tomatoes and simmer for an additional 5 minutes, allowing the sauce to thicken and the tomatoes to soften slightly, enhancing the fresh flavor and texture.
Finish with Cheese and Basil: Remove the skillet from heat and immediately mix in the Parmesan cheese and fresh basil. The residual heat will melt the cheese perfectly while preserving the vibrant aroma of the basil.
Combine Pasta and Sauce: Add the drained pasta back into the skillet and toss well to coat in the creamy sauce. If the sauce feels too thick, gradually add reserved pasta water a tablespoon at a time until the desired consistency is reached. Serve right away, topped with extra Parmesan if you like.