4 tablespoons olive oil, divided
1 large parsnip, peeled, trimmed, cut into 1/2-inch pieces (about 1 1/2 cups)
1 large Granny Smith apple, peeled, cut into 1/2-inch pieces (about 1 3/4 cups)
2 teaspoons chopped fresh thyme plus sprigs for garnish
4 6- to 8-ounce skinless boneless chicken breast halves, pounded to 1/2-inch thickness
1 cup dry Sherry
2 tablespoons butter
Heat 2 tablespoons oil in heavy large skillet over medium-high heat. Add parsnip; sauté until beginning to brown, about 2 minutes. Add apple and chopped thyme; cook until parsnip and apple are tender, about 6 minutes. Transfer parsnip mixture to plate.Sprinkle chicken with salt and pepper. Heat remaining 2 tablespoons oil in same skillet over medium-high heat. Add 2 chicken breasts; sauté until cooked through and golden, about 3 minutes per side. Transfer chicken to platter; tent with foil to keep warm. Repeat with remaining 2 chicken breasts.Add Sherry to same skillet. Stir over medium-high heat, scraping up browned bits. Add parsnip mixture and cook until liquid is reduced by half, about 2 minutes. Remove from heat and stir in butter. Season sauce with salt and pepper. Spoon over chicken; garnish with thyme sprigs.