Butter one side of each slice of bread generously.

In a skillet big enough to hold them, cook the slices butter side down over medium heat, just until pale gold on one side. Cover two of the slices with chocolate. Flip a naked slice on top, butter side up.

Cook, turning the sandwiches as necessary, until the chocolate is softened and the sandwiches are browned on both sides.

Serve immediately, sprinkled with a pinch of sea salt or a dusting of cinnamon sugar, if you like.