How to make Marcus Wareing’s croque monsieur

Ingredients

Method

1. Start by making the béchamel. 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 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 and stir quickly to combine. 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 200°C/180°C fan/gas 6.
3. Place the grated Gruyère on one slice of the sourdough then top with the prosciutto. Finish with the béchamel then top with the other slice of sourdough. Heat a frying pan over medium heat. When hot, add the butter then carefully add the sandwich and toast it for three to five minutes. Gently turn the sandwich over and brown the other side for another three to five minutes.
4. Transfer to a piece of baking parchment on a baking tray and bake in the oven for four to five minutes, until the cheese has melted.