You add the cream after you have sauteed the asparagus, mushrooms, and garlic in olive oil. Your eyes will tell you when the garlic gets to be golden brown, as well as your nose will smell the garlic aroma.
When adding the Cream/Veggie Stock/White Wine it is called deglazing the pan. It is done for 2 reasons 1. it gets the most flavorful bits from the bottom of the pan and 2. it leaves the pan a LOT easier to clean when finished. Use a wooden spoon to keep your pots and pans in good shape. Hope I helped.