Drain the tuna well and then mash it very finely with a fork. Finely dice the onion and add to the tuna with the crème fraiche and parsley. Season well with freshly ground (coarse) pepper and salt and mix.
If you like, you can also add a touch of garlic powder.
Tastes good with ciabatta, flatbread, vegetable sticks or as a spread on brown bread.