Chop the ham and onion and place in a bowl. Add the crème fraîche and the grated cheese and season the mixture with salt and pepper. Mix everything together, if the mixture is too firm, dilute with a little cream / milk. The mixture should be easy to spread on the toast, but not run.
Place the coated toast on a wire rack or a baking tray and bake in the oven at approx. 160 ° C for approx. 10 - 15 minutes (to taste).