Preheat the oven to 375 degrees F. Heat the oil in a skillet over medium heat. Add the onion and garlic and cook 3 to 4 minutes; add the tomatoes, stock, basil and sugar. Bring to a gentle simmer and cook five minutes. Grill or pan-fry the sausage until nicely coloured, but not cooked through. Season the tomato mixture with salt and pepper, and then pour into a 9 x 13-inch casserole. Set the sausages into the casserole. Surround the sausages with artichokes and olives. Cover and bake 30 minutes. Serve sausage over pasta, if desired.