Return turkey to Dutch oven, increase heat to high, and add thyme sprig and stock to cover. Bring to a boil, then reduce heat to medium-low and simmer gently, covered, for 1 1/2 to 2 hours, until meat begins to fall from turkey bone. Transfer turkey legs to plate using fork, remove skin, and separate meat from bone. Remove thyme sprig.
Return meat to Dutch oven. Discard bones and skin. Add carrots and parsnips and simmer, uncovered, on medium for about 30 to 40 minutes, until vegetables are tender.
Just before serving, add frozen peas, stir through, and simmer for 5 minutes to heat thoroughly. Taste and adjust seasoning, if required, with remaining salt and pepper. Serve stew in shallow dishes, sprinkled with tarragon and accompanied by crusty bread, or over rice.
Recipe Notes
Per serving: 313 calories; 35 g protein; 9 g total fat (3 g sat. fat); 24 g total carbohydrates (8 g sugars, 7 g fiber); 459 mg sodium