Melt the butter in a large skillet over medium-high heat. Add the chicken and cook until browned on both sides. When the chicken is browned, transfer to a 13 by 9-inch baking dish.

To the same skillet, add the broth and lemon juice. Scrape the bottom of the skillet to incorporate the pan juices into the broth and juice. Simmer over low heat for 2 - 3 minutes. Add the mushrooms, green onions, lemon zest, parsley, salt, and pepper to the skillet and stir well. Remove from the heat and stir in the sour cream. Pour the mixture over the chicken in the baking dish.

Bake, uncovered, for 1 hour. Let cool for 10 minutes before serving. Garnish with sliced green onions, if desired.