If you haven't soaked the Porcini in advance (see note below) set combine Porcini and water in a saucepan and bring to a simmer; let soak for 20 minutes or until tender. Drain soaked Porcini, rinse them to remove grit; and chop them. Strain the soaking liquid through non-bleached paper towel or cotton cheesecloth-lined sieve; reserve for later.
Heat the olive oil in a saucepan. When hot add chopped soaked Porcini and saute for a few seconds. Add the fresh mushrooms, cover and cook over very low heat until mushrooms are tender (if they begin to stick to the bottom of the pan, add a few spoonfuls of mushroom soaking liquid). Add reserved Porcini liquid and broth and bring to a simmer; add tortellini and cook, uncovered for 5 minutes or until tender. Season to taste with salt and pepper and portion out; garnish with chives.
NOTE - to soak mushrooms in advance; cover 2 ounces of dried mushrooms with 1 quart of water; set in refrigerator overnight or for longer; remove soaked mushrooms and soaking liquid as needed.