To make the crab cakes: Pick through the lump crab for shells (VERY GENTLY).
In a saucepan over moderate heat, sweat the onion and pepper in the butter. Remove from heat and cool.
In a stainless bowl mix the egg, mayonnaise, mustards, parsley, cayenne, hot sauce, salt and pepper. Add in onions and peppers and fold in the crabmeat. Form into cakes about 3 inches across by 1 and 1/2 inches thick. Pack firmly, but do not crush the lumps, the cake should just hold together. Dredge on top and bottom in bread crumbs and chill for at least 1 hour in the refrigerator.
Preheat an oven to 400 degrees F.
In a saute pan over medium high heat, add 2 tablespoons of the vegetable oil and when hot, saute the crab cakes on 1 side. Do not crowd the pan. Do it in batches if serving several. Add a nut of whole butter to the pan and cook the cakes until brown on the other side. Place in the oven for about 2 to 3 minutes to heat through.
To make the creme fraiche: Mix all ingredients together and serve at room temperature. This will keep refrigerated for 3 to 4 days.