Rinse the chicken pieces in cold water and pat dry with paper towels. Place the chicken into a large bowl, add in tarragon, garlic, salt, pepper, oil, and vinegar. Mix everything to make sure the chicken is coated in the seasonings and spices. Leave it in the refrigerator for at least 1 hour. Get it out from the refrigerator 15 minutes before starting to cook
In a Dutch oven, preheat 4 Tbsp of grape seed oil. In batches, place the chicken pieces in the pot and brown each pieces for about 3 minutes each side. Don't overcrowd your pot or the chicken won't brown properly. Place on a plate. Preheat your oven to 350 F
In the same pot, arrange the potato slices in one layer covering the bottom of the pot, follow by onion slices, then bell pepper slices and then the chicken slices. Continue until you end with potatoes on the top layer. Pour in the chicken stock and bring it to a boil. Turn off the heat. Scatter the olives on top. Cover the pot with the lid and bake in the oven for about 1 to 1 1/2 hours or until the chicken is cooked through