Preheat your oven to 190°C (170°C fan) and bring a large pot of salted water to a rolling boil. You'll hear the water roaring and see steam rising steadily — that's your cue it's ready. Cook the pasta for 2 minutes less than the packet suggests, as it will finish cooking in the oven. Drain and toss with a drizzle of olive oil to stop it clumping together.

While the pasta cooks, season the chicken chunks generously with salt, pepper, and paprika. In a large frying pan over medium-high heat, melt half the butter until it sizzles and foams — you'll hear that gentle hiss and see the butter turn a pale golden colour. Add the chicken in a single layer, not overcrowding the pan. Cook for 5-6 minutes, turning occasionally, until the pieces are golden brown on all sides and feel firm to the touch. Transfer to a plate — you'll see a lovely caramelised crust on the chicken.

In the same pan, add the remaining butter and the chopped onion. Stir and let it cook over medium heat for about 4 minutes until the onions turn translucent and release a sweet, fragrant aroma. Add the minced garlic and cook for another 30 seconds until you can smell that unmistakable garlicky warmth.

Sprinkle the flour over the onion mixture and stir continuously for 1 minute. You'll see it form a thick paste that pulls away from the sides of the pan — this is your roux. The raw flour smell will disappear, replaced by a nutty, toasty scent. Slowly pour in the chicken stock while whisking vigorously to prevent lumps, then add the double cream in a steady stream. The sauce will start to thicken after about 3 minutes of gentle bubbling — look for it coating the back of a spoon thickly.

Stir in the Dijon mustard, half the grated Swiss cheese, and half the Parmesan. Keep stirring until the cheese has completely melted and the sauce is smooth and glossy, with a pale golden colour. Taste and adjust seasoning — the sauce should be rich and savoury with a gentle mustard warmth.

Combine the cooked pasta, browned chicken, and diced ham in a large mixing bowl. Pour the cheese sauce over everything and fold gently until every piece is coated — you'll see the sauce clinging to each shape and the colours of chicken, ham, and pasta coming together evenly.

Transfer the mixture into a 9x13 inch baking dish and spread it into an even layer. Sprinkle the remaining Swiss cheese and Parmesan over the top, creating a thick, even blanket. The dish will look full and inviting, with the sauce peeking through the cheese topping.

Bake uncovered for 25-30 minutes. After 20 minutes, check the surface — you're looking for a deep golden brown crust with bubbling edges. The cheese should be melted completely, with darker spots forming on the peaks. Let it rest for 10 minutes on the counter before serving — you'll see the sauce settle and become creamier as it cools slightly. Garnish with fresh parsley just before bringing it to the table.