baguette or sourdough sliced to approximately 1/4 inch then toasted
butter cut into small cubes and kept chilled
in a hot saucepan put oil then sliced onions and cook gently in low to medium heat, seat with salt and pepper and thyme. Once onions are soft and caramelized, add beef stock, then simmer for 10-15 minutes or until the broth has slightly thickened.Slowly add cold knobs of butter then season with salt, pepper and sugar if more sweetness is needed.
Place soup in oven proof bowls, top with bread and grated gruyere cheese. Turn on broiler function of oven and gratinate Cheese. expect the soup to bubble up and cheese to slightly spill over. Once cheese has been gratinated, soup is ready to serve.
*You can also use an oven toaster to gratinate the cheese