Croque Monsieur

The Croque Monsieur is the bistro toasted sandwich done properly: good ham layered with nutty Gruyere, bound by a mustardy bechamel and gilded under the grill. It is rich, crisp and deeply savoury, and far quicker than its reputation suggests.

Forget the sad cheese toastie: a real Croque Monsieur is a small act of French confidence. You build a quick mustard-spiked bechamel, layer ham and Gruyere between buttered bread, then blanket the top with more sauce and cheese before grilling until bronzed and bubbling. It eats like a hot souffle sandwich, and it is genuinely easy.

Ingredients

• 4 slices white bloomer or sourdough bread — day-old is ideal, cut medium-thick
• 25 g unsalted butter — for the bechamel, plus extra soft butter for the bread
• 20 g plain flour
• 250 ml whole milk — warmed
• 1 tsp Dijon mustard
• 1 pinch freshly grated nutmeg
• 120 g Gruyere — grated; Comte or Emmental also work
• 4 slices good-quality cooked ham — roughly 120 g, thick-cut if possible
• 1 tbsp finely grated Parmesan — optional, for the top
• to taste fine sea salt and black pepper

Method

1. Melt the 25g butter in a small saucepan over a medium heat, then stir in the flour and cook for 1-2 minutes to a pale, sandy paste, without letting it colour.
2. Take the pan off the heat and gradually whisk in the warm milk a splash at a time, returning it to the heat once smooth. Simmer gently for 3-4 minutes, whisking, until thick enough to coat the back of a spoon.
3. Stir in the Dijon, nutmeg and a small handful of the Gruyere. Season with salt and pepper, then set the bechamel aside; it will thicken further as it stands.
4. Heat the grill to high and line a baking tray. Lightly butter one side of each bread slice and place two, buttered-side down, on the tray.
5. Spread a thin layer of bechamel over the two slices, then add the ham and about half the remaining Gruyere. Top with the other bread slices, buttered-side up.
6. Spoon the rest of the bechamel generously over the tops, letting it spill slightly down the sides, and scatter with the remaining Gruyere and the Parmesan.
7. Grill about 10cm from the element for 4-6 minutes, until the top is deeply golden and bubbling and the cheese has caught in places. Watch closely so it browns rather than burns.
8. Rest for a minute, then cut each sandwich in half and eat while the cheese is still molten.

Serve it with

• A sharply dressed green salad with mustard vinaigrette
• Cornichons and Dijon on the side
• Thin fries or pommes allumettes
• A bowl of tomato soup
• A cold glass of dry cider or white wine

Why this works

The bechamel does double duty: inside it keeps the sandwich luxuriously moist, while on top it browns into a savoury, souffle-like crust that a slice of cheese alone can never achieve.

Common swaps

• Turn it into a Croque Madame by frying an egg and setting it on top
• Swap Gruyere for Comte, Emmental or a mature Cheddar at a push
• Use wholegrain mustard for a coarser, punchier bite
• Try cooked turkey or good-quality wafer-thin ham if that is what you have

Common mistakes to avoid

• Skimping on the top bechamel and cheese, so it never forms that signature golden crust
• Using thin, floppy sliced bread that collapses under the sauce
• Grilling too close to the element, scorching the top before the middle heats through
• Rushing the roux, leaving a raw-flour taste in the sauce

Storage, freezing & reheating

Storage: Best eaten straight away, but assembled unbaked sandwiches keep, covered, in the fridge for up to a day. Leftover bechamel keeps for 2 days.

Reheating: Reheat a cooked croque in a hot oven or air fryer at 180C for 6-8 minutes to re-crisp; microwaving turns the bread leathery.

Allergen notes: contains Milk, Gluten, Mustard. Always check individual product labels.

Estimated nutrition

Per serving, estimated from typical ingredient values — not a substitute for precise dietary calculation.