Marcus Wareing’s guide to the perfect croque madame – and why a roux is key

“A classic roux sauce is the foundation for so many great recipes and although I didn’t learn about it until I went to college, it’s one of the first things my wife Jane taught our kids to make when they were young,” says Marcus Wareing.

“It opens so many culinary doors: macaroni cheese, lasagna, moussaka and arguably the best sandwiches in France – croques monsieur and madame. Layers of cheese, ham and luxurious roux sauce sandwiched between two slices of bread, toasted in butter and – in the case of the croque madame – topped with a perfectly fried egg.

“Sandwiches may have been invented in Great Britain, but the French really took them to a whole new level with this fabulous recipe.”

Croque madame

Serves: 2

Prep time: under 10 minutes | Cooking time: 20 minutes

Ingredients:

100g Gruyère cheese, grated

4 slices of sourdough

4 slices of prosciutto

1 tbsp butter

Vegetable oil, for frying

2 eggs

Watercress or lamb’s lettuce, to serve

For the roux sauce:

200ml milk

2 tsp fresh thyme leaves

2 tbsp butter

2 tbsp plain flour

1 tsp Dijon mustard

2 tsp wholegrain mustard

100g Cheddar cheese, grated

Sea salt and freshly ground black pepper

Method:

1. Start by making the roux sauce. Put the milk and thyme into a small saucepan. Gently bring to a simmer over low heat. Melt the butter in another small saucepan, then add the flour and a pinch each of salt and pepper. Cook over a low heat for about one minute to get rid of the floury taste but avoid letting it brown. Gradually whisk in half of the hot milk, then add the remaining milk and cook for a further five minutes over low heat, stirring continuously. Remove from the heat, add the mustards and cheese and stir until the cheese has melted.

2. Preheat the oven to 200C/180C fan/gas 6 and line a baking tray with baking parchment.

3. Divide the grated Gruyère between two slices of the sourdough, then top with the prosciutto. Finish with two-thirds of the roux sauce then top with the other slices of sourdough. Spread the remaining roux sauce on top. Heat a large frying pan over medium heat. When hot, add the butter then carefully add the sandwiches and toast them for three to five minutes. Gently turn the sandwiches over and brown the other side for another three to five minutes.

4. Transfer to the lined baking tray and bake in the oven for four to five minutes until the cheese has melted.

5. While the sandwiches are baking, heat a little vegetable oil in a frying pan and crack both eggs into the pan. Fry for two to three minutes, or until the white is set and the yolk is still soft.

6. Place the sandwiches on two separate plates and top each with a fried egg. Serve with watercress or lamb’s lettuce on the side.

‘Marcus’s France’ by Marcus Wareing (Harper NonFiction, £22).