Preheat the oven to 180°C/350°F/gas 4. Cook the macaroni in a pan of salted boiling water according to the packet instructions
Peel the onion and then half it. put the milk in a pan and add the onion, heat over a medium heat.
Remove the onion from the milk. Set the pan aside. in another pan, melt the began butter, then add the flour, string continuously until it forms a paste.
Gradually add the milk, whisking continuously until smooth. Bring to the boil, then simmer for about 10 minutes until the sauce has thickened.
Stir in the nutritional yeast and the mustard and add the grated vegan cheese.
Drain the macaroni and add to the sauce. Transfer the mixture to a baking dish and set aside.
Peel the garlic and finely slice. Discard the stalks of the thyme. Cook with a little bit of olive oil over a medium heat for 2 - 3 minutes. Then put in a food processer with the breadcrumbs and a little bit of oil until chopped and combined. Sprinkle over the pasta
Cook in the oven for 20-25 minutes until the top is golden. Serve with a green salad