1. To make the topping, simply mix all the ingredients together in a large mixing bowl and set aside.
2. In a large non-stick pan on a medium heat, place the butter and flour and whisk quickly and continuously to make a smooth paste for the roux.
3.
Add the milk little by little, continuing to stir to stop lumps from forming. Bring the heat up to high and allow the sauce to thicken whilst continuing to whisk for a further 4 minutes.
4.
Add the mustard, grated Cheddar and Parmesan and mix until incorporated with the sauce. Season with salt and black pepper to taste.
5. Transfer the cooked pasta to the sauce pan and stir well to coat thoroughly.
6. Transfer the cheesy pasta to an ovenproof dish, pouring over any remaining sauce.
7.
Add ‘dollops’ of the Spicy Tomato Salsa and then scatter the torn pieces of mozzarella over the top of that.
8.
Scatter the breadcrumb topping over the top of the dish before arranging the slices of tomato.
9.
Transfer to a preheated oven at 190c (170c fan) for 20 - 25 minutes until the top is golden brown and you can see the cheese sauce bubbling.
10. Serve with an extra dollop of Spicy Tomato Salsa.