Preheat the oven to 180°C. Remove the small wings from the quail (as they look unsightly). Roughly chop 8 slices of pancetta (reserve 8 whole slices for wrapping) and stuff into the quail with the sage. Tie the quail neatly and wrap each with a slice of pancetta.
Heat some olive oil and butter in a pan and sear the quail all over. Add a splash of the white wine and simmer for a few moments. Transfer the quail and pan juices to a baking tray and scatter on the rosemary sprigs, olives and garlic. Cook for 15 minutes until the quail is cooked pink.
Remove from the oven and leave to rest in a warm place while you finish the sauce.
Heat the roasting juices, add the rest of the white wine and chicken stock and simmer until reduced. Whisk in the butter to form a nice glossy sauce. Taste and adjust the seasoning as necessary.
Serve the quail on a mound of white polenta with the sauce and olives.