During a trip to Paris and a visit with master fromager Laurent Dubois, we were reminded just how delicious a well-made croque monsieur can be. Dubois’ version of the iconic French ham and cheese sandwich inspired us to develop a simple, fuss-free recipe that’s doable on a weeknight. A béchamel, or flour-thickened white sauce, is classic, but we take a shortcut and stir together crème fraîche, shredded Gruyère (or Comté) cheese, a couple tablespoons of mustard and small measure of nutmeg. The mixture mimics the sauciness of a roux-thickened béchamel. And instead of griddling the sandwiches one or two at a time, we cook four at once on a baking sheet in the oven. They’re finished with a final slather of “sauce” and a blast of broiler heat for browning. Sliced sandwich bread with a sturdy crumb rather than a soft, cotttony texture is best. We modeled our recipe on Dubois’ three-layer creation, so you will need a total of 12 slices for four sandwiches.