Clean and chop 500 grams of cauliflower into small florets. Boil them in a large pot of water until they are tender, approximately 10 minutes. Drain and set aside.
In a pan, heat 2 tablespoons of olive oil and sauté 1 finely chopped onion and 3 minced garlic cloves until they turn golden brown.
Add the cooked cauliflower, sautéed onion, and garlic to a blender. Add 1 cup of milk, 1/2 cup of grated Parmesan cheese, 1/2 teaspoon of salt, and 1/4 teaspoon of black pepper. Blend until the mixture is smooth and creamy.
If the sauce is too thick, add more milk to achieve the desired consistency.
Pour the cauliflower alfredo sauce back into the pan and heat it on low flame for 2-3 minutes, stirring occasionally.
Serve the sauce over your choice of cooked pasta, and garnish with chopped parsley and additional grated Parmesan cheese, if desired.