In a medium skillet, melt 1 tablespoon of the butter. Add the shallot and cook over moderate heat until just beginning to brown, 4 minutes. Add the vermouth and cook until nearly evaporated, about 1 minute. Remove from the heat and stir in the cream cheese, crème fraîche, mayonnaise, mustard, chives and tarragon. Season lightly with salt and cayenne and scrape into a large bowl. Stir in the crabmeat, breaking it up slightly with a spoon. Spread the crab dip in a shallow baking dish or 12 shallow ramekins.