Trim chicken and pat dry. Season with salt and pepper. Toss in a bag with flour and fry to golden brown in a large skillet. Remove to a baking tray lined with parchment.
Remove rendered fat from pan and coat bottom with olive oil. Fry onions at medium low till soft (5 to 7 minutes).
Add whole garlic cloves to the pan and cook until golden brown
Add vinegar and wine and sugar to the pan a boil for five minutes or until reduced by about half.
Add chicken stock and rosemary to the pan, spooning sauce over chicken.
Cover pan and cook in a 350° F oven for 20-25 minutes. Uncover and cook in oven for another 20-25 minutes.
Remove chicken to a serving plate and cook sauce until reduced by 20 or 30%.
Serve over pasta or mashed potatoes and with a green vegetable on the side.
