Heat the oven to 160C/fan 140C/gas 3. Start with the ragu - toss the beef in the flour and shake off the excess. Heat a little oil in a heavy casserole then brown the beef chunks in small batches until they have a good colour on all sides, then scoop them out and do the next batch.
Once all the beef has browned, tip it back into the casserole and add the onion, carrot and star anise. Cook, stirring for about 5 minutes, then stir in the tomato purée. Add the stock, wine and passata and bring to a simmer. Cover the pan with foil and put on a lid to create a seal. Transfer to the oven and cook for 3 hours, then check the beef is done – you want it to fall apart easily. If it doesn’t, put it back in the oven for another 30 minutes to an hour. Stir in the basil.
Meanwhile, make the mac ‘n’ cheese - melt the butter in a pan then stir in the flour. Keep cooking and stirring for 3 minutes then gradually whisk in the milk to give a smooth sauce.
Add the mustard powder, cheddar, gruyère, emmental and stir until melted. Season.
Turn up the oven to 220C/fan 200C/gas 7. Cook the macaroni until just al dente (approx 7-8 minutes) then rinse under cold water and drain well. Mix with the cheese sauce.
Spoon the ragu into a large baking dish. Top with the mac ‘n’ cheese. Bake for 20-30 minutes until golden and bubbling. Rest for 5 minutes before serving.