1. Cook the pasta

Bring a pot of well-salted water to the boil. Add the pasta and cook until just under al dente, according to packet instructions. Drain and set aside.

2. Cook the bacon

Heat a pan over medium-high heat and cook the bacon until deeply crispy. Transfer to paper towel to drain, then roughly chop into bite-sized pieces. Set aside.

3. Make the roux

Place a large oven-safe pan over medium heat. Add the butter and allow it to melt and foam. Stir in the flour and cook, whisking constantly, until a pale roux forms.

4. Build the sauce

Add the milk a little at a time, whisking well between each addition to keep the sauce smooth. Continue cooking and whisking until the sauce thickens and coats the back of a spoon.

5. Add the cheese

Remove the pan from the heat. Stir through the cheddar, gruyère, Dijon mustard, smoked paprika, salt, white pepper and nutmeg until the cheese is fully melted and the sauce is smooth and glossy.

6. Combine with pasta

Add the drained pasta to the sauce and fold through until evenly coated. Spread the mixture out evenly in the pan.

7. Add the topping and grill

In a small bowl, mix the panko breadcrumbs and parmesan. Sprinkle over the pasta and drizzle with olive oil. Place under a hot grill for 4-5 minutes, or until the top is golden and bubbling and the base starts to crisp.

8. Finish and serve

Remove from the grill and scatter the crispy bacon over the top. Allow to rest for 2 minutes before serving so the base sets slightly and develops a light crust. Serve warm.