Start by cooking the macaroni in a pan of salted boiling water. Once cooked, strain and refresh under cold running water.
At the same time, place the milk into a pan over a low-medium heat and add the thyme and bay. Bring up to a warm heat and leave to infuse for 10 minutes.
Meanwhile, place a separate pan over a low heat and add the butter and garlic. Cook for two to three minutes then add the flour. Heat for two to three minutes and stir constantly, so the mixture comes together.
Add the infused milk, stirring with a wooden spoon, making sure that the roux is properly mixed in and smooth before adding more milk. Once all incorporated, simmer for 2 minutes.
Take the pan off the heat and season with a large pinch of salt and pepper. Add the cheese, mustard, basil and pasta to the pan and then pour the contents into a casserole dish. Cover with some extra cheese and place in the oven at 180C for 20 minutes.
Remove the dish from the oven, divide the macaroni cheese into four portions and serve immediately.