Caramelise the onions by melting the butter in a frying pan over low heat. Add the onions and a pinch of salt and cook, stirring often, for around 40 minutes, or until deeply caramelised. Add the beer and cook for 5 minutes more, or until all the beer is absorbed

Preheat the oven to 180ºC

For the béchamel, warm the whole milk in a saucepan over medium heat (this isn’t strictly necessary but will help the milk emulsify better with the butter and ensure your sauce is lump free)

Melt the butter in a separate saucepan (large enough to hold all the milk) over medium heat and, once foaming, add the flour. Whisk this together for a couple of minutes, to ensure the flour is cooked out properly

Gradually add ladlefuls of the warm milk, whisking each to incorporate fully before adding the next

Melt in the miso, white pepper and mozzarella, whisking all the time. Cover and set aside

Lightly toast the bread on both sides and place two pieces onto a baking tray. Spread two pieces of bread generously with Dijon mustard, then top with the ham hock, caramelised onions and then grated Comté or Gruyère

Top with the remaining pieces of bread, then a thick layer of the béchamel. Bake at 180ºC until the cheese is all melted and it’s warm in the centre (you can test this by probing it with a skewer to see if it comes out warm). It’ll probably take 15 minutes

Immediately place the sandwiches under a hot grill to get the top golden. They should be bubbling and have brown spots on top

Heat a frying pan with a splash of oil and fry the eggs, then serve on top of the sandwiches

Serve with extra Dijon and the cornichons!