Fill a large cooking pot with water and bring to the boil over a high heat. Add the macaroni and cook until al dente, for about 12 minutes.
Preheat the oven to 400°F. Grease three individual portion ramekins or ovenproof dishes.
Melt the butter in a saucepan over a medium high heat with the thyme leaves and then whisk in the flour. Cook for 2 minutes and then pour in the milk. Continuously whisk until the mixture comes to a steady simmer and continue to cook until you have a thick sauce.
Add the wholegrain mustard, a pinch of nutmeg and three-quarters of the cheese, and season with sea salt and ground black pepper. Mix through until the cheese has melted. Pour the cheese sauce over the pasta in the pot and mix through until everything is combined. At this point you can play around with the flavours and add them at this point before baking off in individual serving pots.
Divide the pasta between the 3 dishes.
For the classic version leave as is.
To make the chorizo version, cut the chorizo into cubes and fry in a little oil until crispy, fold into the pasta with a teaspoon of smoked paprika.
To make the bacon version, fry the streaky bacon in a little oil until crispy. Break into pieces and fold through the last dish, with a small handful of chopped basil leaves.
Sprinkle the dishes with the remaining cheese and pop in the oven to cook for 25 minutes or until the top has turned golden and the sauce is bubbling up the sides. Remove from the oven and allow to cool slightly before serving in big, deep bowls.