Place Porcini in a spice or coffee grinder, process until finely ground.
Slice chicken breasts halves in half horizontally. Sprinkle chicken with 1/4 tsp salt and pepper. Sprinkle both sides with porcini powder, shaking off excess.
Heat 1 tsp oil in a large non stick skillet over medium high. Add chicken pieces to pan, cook 1 1/2 minutes a side or until lightly browned and done. Remove from pan, keep warm. repeat until all are done.
Heat remaining tsp or so of oil in pan. Add shallots and garlic, cook 1 minute stirring. Add 3 cups mushrooms, cook 5 minutes until liquid evaporates, stirring occasionally. Add wine, scraping brown bits to loosen. Increase heat to medium high. cook 2 minutes until liquid almost evaporates.
Add broth to pan, simmer until mixture is reduced to 1/4 cup (about 5 minutes). Stir in sour cream, cook 1 minute. Remove from heat. Add salt, pepper and parsley.