Clean the asparagus by snapping off the tough base of each spear, this is usually around the bottom third of the spear, where the stem starts to turn tender. Keep only the tender part. Chop into ¼ inch (¾ cm) size pieces (separate the heads from the stems).
In a small to medium pot, cook the heads in boiling water for approximately 5 minutes, remove with a slotted spoon and set aside.
Boil in the same water the cut up stems for 10-15 minutes or until tender. With a slotted spoon remove the stems, DO NOT THROW AWAY THE WATER, and place in a blender with a 1 cup of the boiled asparagus water. Blend until smooth.
In a large frying pan add the olive oil, butter, garlic, shallot and cut up sausage, cook for approximately 10 minutes, until the sausage is no longer pink, then add the tomato puree, pepper or hot pepper flakes, blended asparagus and asparagus heads,(add salt if desired) cook on low to medium for approximately 10-15 minutes, stirring often.
Add the cooked pasta al dente, and ¼ cup of pasta water, toss gently to combine while heating on high heat until thickened (approximately 30-60 seconds). Serve immediately topped with freshly grated parmesan cheese if desired. Enjoy!
Notes
Pasta usually doubles in size when cooked, so for the recipe you will need approximately 1 1/2 to 2 cups of dried pasta to make 3 cups cooked. One cup of uncooked pasta is equal to approximately 70 grams (I measured with mezze rigatoni).Cream sauces I was taught in Italy should always be served with a short pasta, such as Penne, Mezze Maniche, Fusilli, Rigatoni, Tortiglioni, or Sedani and if you ask the Italian he will tell you to make sure you get Rigati Pasta (pasta with ridges), it will hold the sauce better!Any leftovers should be stored in an airtight container and refrigerated. It will keep for 2-3 days in the fridge. Heat the leftovers, on the stove or microwave.