Step 1

Place dried shiitake mushrooms in a small heatproof bowl; cover with boiling water. Let stand 20 minutes. Drain, reserving mushrooms and 1 cup soaking liquid. Set aside.

Step 2

Prepare noodles according to package directions, omitting salt and fat. Drain; rinse noodles under cold water and drain again. Set aside.

Step 3

Melt butter in a large skillet over medium-high. Add soaked shiitake mushrooms and fresh mushrooms to skillet in an even layer; cook, stirring occasionally, until well browned, 16 to 18 minutes. Add onion, garlic, thyme and tarragon; cook, stirring occasionally, until onion is tender, about 4 minutes. Add flour; cook, stirring often, 1 minute. Add stock, reserved mushroom soaking liquid, mustard, salt and pepper; let come to a boil. Boil, stirring occasionally, 2 minutes. Remove from heat; let cool 5 minutes. Stir in sour cream. Stir in cooked noodles; sprinkle with cheese and parsley.