Place porcini mushrooms in a spice or coffee grinder; process until finely ground. Slice chicken breast halves in half horizontally. Sprinkle chicken pieces with 1/4 teaspoon salt and 1/8 teaspoon pepper. Sprinkle both sides of chicken with porcini powder, shaking off excess powder.
Heat 1 teaspoon oil in a large nonstick skillet over medium-high heat. Add 4 chicken pieces to pan; cook 1 1/2 minutes on each side or until chicken is lightly browned and done. Remove chicken from pan; keep warm. Repeat procedure with 1 teaspoon oil and remaining 4 chicken pieces.
Heat remaining 1 teaspoon oil over medium heat. Add shallots and garlic to pan; cook 1 minute, stirring frequently. Add 3 cups mushrooms; cook 5 minutes or until liquid evaporates, stirring occasionally. Stir in wine, scraping pan to loosen browned bits. Increase heat to medium-high; cook 2 minutes or until liquid almost evaporates. Add broth to pan; simmer until liquid is reduced to 1/4 cup (about 5 minutes). Stir in sour cream; cook 1 minute. Remove from heat; stir in remaining 1/4 teaspoon salt, remaining 1/8 teaspoon pepper, and parsley.
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