Peel the onions and cut them into half rings, except for 15-20 g. Wash the thyme, shake dry and pluck the leaves from the stems. Heat 4 tablespoons of oil and butter in a saucepan, fry the onions for about 10 minutes, stirring continuously. Add sugar and steam for another 3-5 minutes until the onions start to brown.
Pour in beef stock and vegetable broth, bay leaf and thyme, except for something to sprinkle, add and bring to the boil. Cover and simmer for 10-15 minutes
Finely crumble the toast with a chopping stick. Peel garlic and chop finely. Chop the remaining onion (15-20 g) finely. Knead minced meat, toast, onion, garlic, tomato paste, parmesan, salt and pepper. Form about 16 small meatballs. Heat 1-2 oil in a frying pan, fry the balls for about 4 minutes, turning them over, and take them out
Dab mozzarella dry and dice finely. Mix with the Gruyère cheese. Place baguette slices on a baking tray lined with baking paper and spread meatballs on top. Sprinkle with cheese and gratinate under the preheated grill for 4-5 minutes. Season soup with salt and pepper and arrange in deep bowls with the cheese baguettes. Sprinkle with remaining thyme leaves