Cucumber wash, clean and cut into cubes. Peel onion and cut or slice into thin rings. Mix vinegar, salt, pepper and sugar. Allow oil to run in in a thin stream while stirring. Mix cucumber cubes with the vinaigrette. Season to taste with salt, pepper and sugar
Cut white bread slices horizontally in half with a saw knife, cutting only deep enough to halve the slices, but not to separate them. Place two slices of ham and cheese between each slice
Whisk eggs with milk. Season with salt and pepper. Press the slices of white bread well and dip them into the egg milk from both sides so that they are slightly soaked
Heat 1 teaspoon of clarified butter in a coated pan and fry 2 slices of white bread on each side for 2-3 minutes on medium heat until golden brown. Remove the slices from the pan. Process remaining slices in the same way. Cut the toast cordon bleu diagonally in half and arrange on plates. Add cucumber salad