For the topping, heat the oil in a frying pan over medium heat. Add the breadcrumbs and toss them frequently in the pan until they are a light golden colour, 5-10 mins. Remove from heat and cool slightly, then add garlic, parsley and lemon zest and mix through the crumb. Season with salt and pepper and put aside.

Melt butter in a large saucepan and add onion. Cook over medium heat and sweat, stirring regularly for 6-8 mins until the onions soften. With a wooden spoon, stir in flour to make a roux. Continue to stir for 1-2 mins to cook out raw flour taste. Little by little, whisk in milk. Keep whisking until there are no lumps and bring to gentle boil until it thickens. Take off heat and mix in cheeses, mustard, spices and salt and pepper.

Bring a large pot of salted water to boil. Add pasta and cook until al dente. Drain well.

Fold pasta into sauce, coating well, then fold in ham.

Portion mac n cheese and then sprinkle over with topping.