adapted from: Cook's Illustrated
2 Lbs. boneless, skinless chicken breasts
salt and pepper
1 Tbl. unsalted butter
1 Tbl. olive oil
1 Lb. mushrooms, washed and sliced or chopped
1 onion, chopped fine
1/4 c. dry white wine (I used chicken broth)
1 Tbl. all-purpose flour
1 garlic clove, minced
1 1/2 c. low-sodium chicken broth
1/3 c. sour cream
1 large egg yolk
1/2 tsp. freshly grated nutmeg
2 tsp. lemon juice
2 tsp. minced fresh tarragon or parsley
Pat dry chicken with paper towels and season with 1 teaspoon salt and 1/2 teaspoon pepper. Heat butter and oil in 12-inch skillet over medium-high heat until butter is melted. Place chicken in skillet and cook until browned, about 4 minutes. Using tongs, flip chicken and cook until browned on second side, about 4 minutes longer. Transfer chicken to a large plate. Add mushrooms, onions and wine to now-empty skillet and cook, stirring occasionally, until liquid has evaporated and mushrooms are browned, 8-10 minutes. Add flour and garlic; cook, stirring constantly, 1 minute. Add broth and bring mixture to boil, scraping up browned bits from bottom of pan. Add chicken and accumulated juices to skillet.
Reduce heat to medium-low, cover, and simmer until breasts register 160 degrees, 5-10 minutes. Transfer chicken to clean platter and tent loosely with aluminum foil. Whisk sour cream and egg yolk together in medium bowl. Whisking constantly, slowly stir 1/2 cup hot sauce into sour cream mixture to temper. Stirring constantly, slowly pour sour cream mixture into simmering sauce. Stir in nutmeg, lemon juice and tarragon or parsley; return to simmer. Season with salt and pepper, to taste. Pour sauce over chicken and serve.
Jenn's Notes: I used one large Costco chicken breast and it was enough for 2 people. I still made the full sauce recipe, because I am a huge sauce person (as you can tell by my picture). The chicken was so moist and flavorful. I used broth instead of wine and parsley instead of tarragon.