For the sauce, place the milk and bay leaves into a pan over a medium heat. Heat to scalding point and then remove from heat.
Meanwhile, in a clean pan over a medium heat, melt the butter. Stir in the flour and cook for 3-4 minutes (don't let the mixture turn brown).
Remove the bay leaves from the milk mixture.
Add a splash of the heated milk to the flour and butter mixture and stir to combine. Continue to heat and stir, gradually adding more milk, until a smooth sauce is formed.
Add any remaining milk and bring to boil, stirring all the time. Reduce the heat and simmer for 3-4 minutes.
Take off the heat and add the cheese, mustard and salt and freshly ground black pepper.
For the pasta, melt the butter in a large frying pan over a medium heat. Add the shallots and cook for 2-3 minutes, then add the cooked macaroni and cherry tomatoes, and the pre-prepared cheese sauce. (You may need to add a little extra milk to loosen the cheese sauce.) The sauce should coat, but not drown the macaroni.
Divide the macaroni cheese evenly among four ovenproof bowls and top with grated parmesan. Place into the oven to bake for 8-10 minutes.
Preheat the grill to its highest setting.
Remove the individual macaroni cheese bowls from the oven and place under the grill until the cheese topping is bubbling and golden-brown.
Serve at the table in the cooking bowls. Be careful - the bowls will be very hot!