Chop the onions, garlic, and set aside. Chop the leek (cut in 1/2 lengthwise first & make sure to rinse very well!!) and set aside (separate from the onions & garlic). Chop the sage & set aside separately as well.
To easily remove the casings, lightly slice each sausage lengthwise. Peel off with your fingers. In a large pan over medium/high heat, cook the sausages until they are a nice golden brown. While cooking, break apart the mixture until it looks like ground meat.
Take the meat out of the pan and save it in a bowl.
Add 2 tbsp olive oil and add the sage to the pan. Cook for a minute, add the leeks & cayenne pepper. Cook for 2 to 3 minutes and put the meat back in the pan. When the leek is cooked, turn off the heat and keep in the mixture in the pan.
In a medium size pot over medium/ high heat, add 1 tbsp olive oil, thyme, garlic & onions. Cook for 3-4 minutes, until onions are translucent.
Add crushed tomatoes, lower the heat and simmer for about 20 minutes (with a lose lid, otherwise the sauce will splatter all over your kitchen walls!)
Add sugar and about 1 tsp kosher salt (1/2 tsp for regular salt), stir and cook for another 2 minutes. Puree the tomatoes until smooth.
Add milk and butter, and stir. Keep the heat on very low or turn off until you are ready to serve.
When rigatoni is cooked, add to the hot pan with the sausage mixture. Stir well, add a little olive oil if it looks dry. Plate and add tomato sauce to the pasta.
