Put the first 5 ingredients in a bowl, squeeze the garlic and stir everything together.
Halve and slice the cucumber, quarter the lettuce hearts and cut into thin strips. Halve or quarter the cocktail tomatoes depending on their size, peel and grate the carrots, halve the onions and cut into thin slices, finely dice the ham and Gouda cheese, cut the eggs into eighths.
Arrange the lettuce hearts on 4 large plates, spread the onions, cucumber, carrots and tomatoes on top and drizzle with the sauce. Cover each plate with 1 tablespoon corn, 1 slice of ham and Gouda cheese and the egg. Spread the tuna and pour a few more dabs of sauce over it.
If you like, you can stir 2 tablespoons of cognac into the sauce.