Cook the pasta according to the package instructions in a large pot of salted boiling water until al dente. Drain and set aside, reserving about 120 ml of pasta water. In a separate pan, heat olive oil over medium heat. Add minced garlic and chopped onion, sautéing until softened and fragrant, about 3-4 minutes. In a small bowl, whisk together low-fat milk and all-purpose flour until smooth. Pour the mixture into the pan with the garlic and onion, stirring constantly until it starts to thicken, about 2-3 minutes. Reduce the heat to low and add grated Parmesan cheese to the sauce, stirring until the cheese is melted and the sauce is creamy. Season the sauce with salt and pepper to taste. If the sauce is too thick, you can thin it out with a little bit of reserved pasta water until you reach your desired consistency. Add the cooked pasta to the sauce, tossing until the pasta is well coated. Serve the creamy low-fat milk pasta hot, garnished with fresh chopped parsley or basil.