1: Melt the butter in a small saucepan over a medium heat, then add the flour and cook, stirring gently, for 1 minute. Gradually add the milk, whisking well after each addition. Keep whisking gently over the heat for 3–4 minutes or until the béchamel sauce is simmering and thickened. Season with salt and pepper to taste.

2: Transfer the béchamel to a bowl, cover the surface with a piece of baking paper to prevent a skin forming and place in the fridge to cool down.

3: Preheat the oven to 220°C/Fan 200°C/Gas 7. Line a baking tray with baking paper.

4: Toast the sourdough slices and spread with your favourite mustard on one side. Mix the grated cheeses together. When the béchamel is cool, spoon a layer on top of the mustard and add a sprinkling of cheese. Add a layer of ham and then spread with the rest of the béchamel and sprinkle on a final layer of grated cheese.

5: Pop the cheese and ham toasts on the lined baking tray and place on the top shelf of the oven. Cook for around 8 minutes until the cheese is golden and bubbling on top. If you want some more colour on the cheese, place under the grill for the final 1–2 minutes.

6: Serve the croque monsieur with a mixed leaf salad alongside and some cornichons to cut through the richness.