To make the caramel: Using a food processor, pulverize the granulated sugar into fine powder/dust. In a pot, heat water on medium. As water begins to slowly heat, carefully pour pulverized sugar into the center of the pot, creating a mound. Do not touch or mix the sugar into the water, let it dissolve on its own. Once sugar-water begins to boil, keep a close eye on it: in a few minutes the water will boil away and then the sugar will begin to boil. Watch closely, the second the molten sugar begins to turn a light brown/caramel color, take it off the heat and add whipping cream and butter. Careful, it will spatter. Whisk until smooth. Add a big pinch of fleur de sel and whisk some more.
To make the French toast: In a big bowl, combine eggs, milk, vanilla bean, sugar, and sea salt. Beat these ingredients together. In a frying pan, heat the unsalted butter over medium heat. Fry the bread for about 1 minute per side or until golden. Turn the heat down to medium low and cook for 1 to 2 minutes on each side.
Serve the French toast in stacks slathered with caramel and topped with a dollop of crème fraiche or sour cream.