Peel and finely chop the onion. Wash the tomatoes, dab dry and also cut into small cubes. Mix vinegar, salt, pepper and mustard. Stir in the oil and finally add the diced tomatoes.
Clean lamb's lettuce, wash thoroughly several times and drain well. Mix the lamb's lettuce shortly before serving and serve it separately with the fonudue. Cut bread into not too small pieces. There must be a piece of crust on each cube.
Put bread in a bread basket. Peel and halve the garlic and rub the caquelon with the clove. Remove the rind from the cheese. Grate the cheese on a coarse grater into the caquelon. Pour wine (+ possibly 1 teaspoon fresh lemon juice).
Now place the caquelon on the hotplate and melt it at medium heat while stirring constantly. Stir until the mixture has combined into a creamy cheese cream. Then stir the starch with the kirsch until smooth and finally stir into the fondue.
Stir again for 2 minutes. Then season the fondue with pepper and grated nutmeg and place it on the table Rechaud. Now it must start immediately! Everyone who dips his bread in the fondue should stir once.
So the fondue stays creamy until the end.