Heat 1 Tbsp. oil in a Dutch oven (or large cooking pot) over medium heat. Add chicken and cook, stirring occasionally, until just cooked through, 3 to 5 minutes. Transfer to a plate.Add the remaining 1 Tbsp. oil to the pot. Add onion, potatoes, carrots, rosemary, salt and pepper and cook, stirring often, until the vegetables begin to soften, 3 to 5 minutes. Add broth and apples; bring to a simmer over high heat. Reduce heat to maintain a simmer and cook, stirring often, until the vegetables are tender, 8 to 10 minutes. Return the chicken to the pot and stir in vinegar. Check seasoning and add extra salt or pepper if desired.