Classic Croque Monsieur

Steps

1. Heat the oven to 400°F and

   line (how to line a pan)

   Line a pan Cover the bottom (and sometimes sides) of a pan with parchment or foil so food doesn't stick and lifts out easily. 1. For a sheet pan, tear parchment the size of the pan and lay it flat.2. For a round cake pan, trace the bottom on parchment, cut the circle out and press it in.3. For brownies and bars, leave two long sides hanging over to make handles (a "sling").4. A little grease under the paper holds it in place. Done when: The paper lies flat with no folds where the batter could run under it. How to line a baking pan with parchment: mistakes to avoid

   a sheet pan with parchment.
   400°F
2. Melt 2 tablespoons butter in a saucepan over medium heat,

   whisk (how to whisk)

   Whisk Beat ingredients with a whisk to mix them smoothly or to add air. 1. Use a bowl big enough to whisk without splashing; set it on a damp towel to stop it spinning.2. Hold the whisk loosely and move it in quick circles or side to side, touching the bottom.3. For lumpy mixtures, add liquid a little at a time and whisk after each.4. For sauces on the stove, keep the whisk moving across the whole bottom of the pan. Done when: The mixture is even with no lumps or streaks of egg. How to whisk: mistakes to avoid

   in the flour and cook, whisking, without letting it brown.
   ⏱ Cook flour: 1 min
3. Slowly whisk in the milk and cook, whisking, until the sauce is thick enough to

   coat a spoon (how to coat the back of a spoon)

   Coat the back of a spoon A simple test for when a sauce or custard has thickened enough. 1. Dip a spoon into the sauce and lift it out.2. Turn it over and look at the back.3. Draw a line through the sauce on the spoon with your finger.4. If the line stays clean and the sauce doesn't run into it, it is ready. Done when: The sauce clings in an even, opaque layer and your finger line holds. Safety: Let the spoon cool for a second before you touch it; custards should reach 160°F.How to tell when a sauce coats a spoon: mistakes to avoid

   .
   ⏱ Thicken sauce: 4 min
4. Take the pan off the heat and stir in the nutmeg, salt, pepper and 1/2 cup of the cheese until smooth.
5. Butter one side of each slice of bread. Lay 4 slices buttered side down on the sheet pan, spread them with mustard and layer on the ham and 1 cup of the cheese.
6. Top with the other 4 slices, buttered side up, and bake until the bottoms are golden.
   400°F⏱ Toast: 6 min
7. Flip the sandwiches with a spatula, spread the sauce over the tops and sprinkle with the last 1/2 cup cheese.
8. Bake until the cheese melts.
   400°F⏱ Melt cheese: 5 min
9. Turn the broiler to high and

   broil (how to broil)

   Broil Cook or brown food with strong heat from the top of the oven, like an upside-down grill. 1. Move an oven rack so the food will sit 3 to 6 inches from the heat.2. Turn the broiler on and give it a few minutes to heat.3. Use a metal pan (never glass that isn't broiler-safe) and put the food in.4. Stay at the oven and check every minute; things go from brown to burnt fast.5. Turn the food if the recipe says to. Done when: The top is browned and bubbly or charred in spots, usually in 1 to 5 minutes. Safety: Don't use parchment or wax paper under the broiler; it can catch fire. Use foil or a bare pan.How to broil: mistakes to avoid

   until the tops bubble and brown in spots, watching closely.
   ⏱ Broil: 2 min

Tap an underlined word for how to do it, or see all techniques.

Tips

• Top each sandwich with a fried egg and it becomes a croque madame.
• Gruyère melts smoothly and tastes nutty; Swiss or white cheddar works in a pinch.

Storage

Best eaten hot from the oven. Refrigerate leftovers up to 3 days and reheat in a 350°F oven until hot.

How long leftovers keep, and freezing and reheating: leftovers and storage.