Start by making a mayonnaise:

Whisk the egg yolk with the vinegar, the salt, and the pepper until it has a custard-like consistency.

Add the oil little by little and the mustard, salt, pepper, and white wine vinegar. Add the oil gradually while whisking until the consistency is suitably thick. 

Mix the crème fraîche into the mayonnaise and then the other ingredients.

Adjust the taste with possibly some extra salt, sugar, or lemon juice to your preference.