Butter one side of the sliced bread or cut the side of 6-inch lengths of halved and inverted French bread. Build sandwiches with the buttered sides out; put Camembert, onions and shredded Comte or Gruyere on top of one slice of bread, then cover with remaining slice. Place the sandwich in skillet over medium heat and cover with foil and grill 7-8 minutes. Turn occasionally and press as sandwich turns golden brown. Serve with cornichons and Dijon.