My kids eat a lot of grilled cheese. It’s not a hard recipe per se, but paying attention to the type and thickness of the bread, the use of butter and the type of cheese is critical. A second-rate grilled cheese has too much bread (thin slices only!), the wrong type of cheese and a cooking method that either burns the bread or undercooks it.

During a recent trip to Paris, I visited Laurent Dubois, the master fromager, who has a cheese shop and restaurant on top of the Printemps department store, to get a firsthand lesson in making croque monsieur, the “croque” standing for “crunchy,” which is a tad misleading. Perhaps “toasty” is a better word.

His version is a stripped-down rendition of the original. He uses three thin slices of a round brioche-style bread, one section filled with mustard, grated cheese and ham, and just cheese and ham on the other. The sandwich is then cooked in a heavy-duty griddle with a top that compresses the sandwich as it cooks. His ingredients were perfect, so the result was delicious. But I wondered if a more traditional croque monsieur, which also has a cheesy topping, might be worth investigating.

For starters, classic croque monsieur calls for a béchamel, but that method seemed a tad old-fashioned, so instead, we skipped the cooking and simply mixed crème fraîche, shredded Gruyère or Comté (in Paris, everyone is on the Comté bandwagon; Gruyère is losing its appeal) and a bit of mustard and nutmeg. This avoids the process of whisking together a béchamel, but—and more to the point—this adds flavor. We designed this recipe so that four sandwiches can be baked at a time: butter four slices of bread, flip them over, add the crème fraîche mixture (just one tablespoon per sandwich) and top with ham. Place a second slice of bread on top and repeat with the filling. Finish with a spread of butter on top. We baked them for 20 minutes, flipping halfway through, and then they got a final top slather and a blast under the broiler.

Before we reduced the amount of filling, we were seeing some separation with the cheese. We tried adding flour, but that just gummed up the recipe. A more modest one tablespoon of cheese mixture carried the day.

This creamy, flavorful topping is traditional, and we think it adds a lot of pleasure and personality to what is otherwise just grilled ham and cheese. Two words of caution: Make sure that the entire top of each sandwich has an even slather of cheese mixture, right to the edges (otherwise, the edges can burn before the center is done). And watch the sandwiches like a hawk once they go under the broiler; 10 seconds too long and you are in wildfire territory. As for the bread, supermarket sandwich bread works, but a brioche-style or a Pullman loaf would be better.

Now, back to my kids. Soon after I returned from my Paris trip, I made the recipe for dinner, telling them it was just grilled cheese. Kids are wily—the ruse did not stick. But after the usual chorus of lamentations, they tried it and loved it. And no restaurant critic is tougher than young kids who have yet to adopt the more civilized habits of human behavior.