Cook the pasta | Preheat the oven to 160ºC | Bring a large pan of well-salted water to the boil | Cook the macaroni for 2 minutes less than packet instructions | Reserve a large mugful of pasta water before draining | Set aside

Make the roux | Melt the butter in a large wide saucepan over a medium heat | Add the gochujang and cook for a couple of minutes until fragrant and beginning to caramelise | Stir in the flour and cook out for a minute or two until the mixture comes together

Build the sauce | Add the milk in small batches, whisking constantly and allowing each addition to fully incorporate before adding the next | Bring to a gentle simmer until thickened into a smooth, thick béchamel | Remove from the heat

Finish the sauce | Grate in the cheddar and gruyère, reserving a small handful of both for the top, and whisk until melted | If the cheese isn’t melting, return the pan to a very low heat | Season generously with salt and pepper

Finish the mac | Fold the drained macaroni and sweetcorn into the sauce | Loosen with a splash of pasta water until the sauce coats the pasta without being too thick | Taste and adjust seasoning

Bake | Scatter over the reserved cheese, sesame seeds and crispy onions and bake for a few minutes until the cheese is melted and the top is very lightly coloured | Don’t aim for a crust or the crispy onions will burn | Serve immediately with a sharp green salad