1. Combine 1/2 cup boiling water and mushrooms in a small bowl; cover and let stand 30 minutes or until soft. Drain through a sieve over a bowl, reserving soaking liquid. Finely chop mushrooms.
2. Cook pasta according to package directions, omitting salt and fat. Drain in a colander over a bowl, reserving 1/4 cup pasta water.
3. Combine mushrooms and cream in a medium saucepan over medium heat; bring to a simmer. Stir in salt, pepper, and reserved mushroom soaking liquid; simmer 5 minutes or until slightly thickened. Add pasta and reserved 1/4 cup pasta water to pan; toss well to coat. Sprinkle with cheese and chives. Serve immediately.