Stuffing:
Season the quail with salt and pepper to taste. Make the stuffing by mixing all of the ingredients together in a medium bowl. Divide the stuffing into four portions and stuff each quail with some sausage, securing the quail with a toothpick.
Preheat the oven to 375 degrees. In a large, oven-proof pan, heat the butter until hot, then add the quail, breast side down. Brown the breasts for 5 minutes, then flip onto their backs and baste well with the butter. Place in the oven and roast until the sausage is fully cooked, about 15-20 minutes. Remove the pan from the oven and put the quail on a warm plate. Place the pan over medium heat and add the sage leaves; cook for about 30 seconds, then add the chicken stock, stirring well and scraping the pan with a wooden spoon. Squeeze the lemon into the pan and set aside.
Serve the quail on a bed of mashed potatoes, with the sauce poured over.
