Lock on lid and close pressure valve. Cook at high pressure (most machines default to high) for 0 minutes.
When beep sounds, wait 4 minutes and then carefully release the rest of the pressure.
Remove lid and stir.
Add butter and mix into soup.
If tortellini is firmer than you like, just let the soup simmer until you get the desired softness.
Ladle into bowls and top with grated or shredded Parmesan (or Asiago) cheese and fresh basil, if desired.
Sprinkle half the freshly shredded Parmesan cheese into soup and wait about 30 seconds for it to melt and then lightly stir into soup.
Add the rest of the Parmesan and again, wait for it to melt and then stir into soup.
For a thicker soup, simmer to reduce liquid.As tortellini is very delicate, the bulk of the cooking is done during the time when the pot is building pressure and then after the pot has reached pressure during the time when the pressure is slowly being released. The 0 cook time allows the pot just to reach pressure. This ensures that the tortellini will not break into pieces and stay whole for a nicer presentation.If using dried tortellini, set the pressure cook time to 1 minute and wait 4 minutes before releasing the rest of the pressure.For a softer tortellini, keep pot on warm or use the saute button and allow soup to simmer until desired tenderness.Adding cheese to the pot of soup is optional. I personally do not add it when making the soup just for me, as I like more of a simple and plain tomato soup, much like Campbell's Tomato Soup. (Yes, yes, I know, I don't like to use cans of packaged stuff, but I do like the Cambell's Condensed Tomato Soup.) If you do use shredded cheese (the real stuff, not the stuff in the green can), allow cheese to melt on top of soup for a bit prior to stirring in. This will help to prevent the cheese from clumping on the bottom of the cooking pot.