How to Make It
Heat oil in large, high-sided skillet over medium-high. Sprinkle chicken with pepper and 1/2 teaspoon salt. Cook chicken until browned on 1 side, 4 to 5 minutes. Remove from skillet.
Add rutabaga and 1 tablespoon butter to skillet. Cook, stirring often, until caramelized, 5 to 6 minutes. Add parsnips, onion, and caraway seeds. Cook, stirring occasionally, until browned, 3 to 4 minutes. Add beer, chicken stock, and mustard; bring to a boil over high. Return chicken to skillet, and reduce heat to medium-low. Cover and simmer until a thermometer inserted in thickest portion of chicken registers 155°F, about 10 minutes.
Remove chicken from skillet; cover to keep warm. Cook vegetables, uncovered, until tender, 20 to 25 minutes. Stir in tarragon, vinegar, scallion, remaining 1/2 teaspoon salt, and remaining 1 1/2 teaspoons butter.