Finely dice the onion and garlic. Heat the oil in a large pan over a medium heat, add the beef and cook for 5 mins until caramelised and golden – you’ll need to do this in batches, otherwise the meat will just steam. Remove the beef from the pan and set it aside.

Add another glug of olive oil to the pan before tipping in the onion. Cook for 5-7 mins until golden and translucent. Add the garlic and thyme, cook for 2 more mins, then add the tomato purée. Cook for 1 min. Reduce the heat to low, return the beef to the pan and pour in the milk and beef stock. Season the ragù with black pepper, cover with a lid and simmer for 45 mins, stirring regularly.

Meanwhile, start the sauce by grating all three cheeses. Melt the butter in a large pot and add the flour, cooking for 2-3 mins or until it smells nutty. Gradually add the milk, stirring after each addition, then bring to the boil, reduce to a simmer and cook for 2 mins until thickened. Add the mustard and Parmesan, along with half of the cheddar and mozzarella, then season with salt and pepper.

Heat the grill to high. Bring a large pan of salted water to the boil. Once boiling, add the macaroni and cook for 1 min less than pack instructions. Drain the pasta, reserving a mug of the cooking water. Mix the pasta with the ragu and a slosh of reserved water, mixing well to coat all of the pasta. Transfer to a baking dish and pour over the cheese sauce. Scatter the remaining mozzarella and cheddar on top and put under the grill for 5-10 mins until bubbling and golden.