Half fill a large pan with water, add a pinch of salt and a glug of olive oil. Add the pasta when the water starts to boil, after 10 minutes take a piece of pasta out and if when bitten it is soft on the outside but just a little undecooked on the inside it is ready. Drain and run under the cold tap so it doesnt cook any more, put back in the pan and drizzle with a little olive oil, mix it around so that the pasta doesn't stick and put to one side for later.
For the sauce; add the butter to a heavy bottom non stick saucepan on a medium heat, when the butter has melted and starts to foam add the flour and mix in with a wooden spoon. After a minute or two the mixture will start to turn light brown and at this stage add a small amount of milk and mix together, keep adding small quantities of milk and mixing until you have a mixture the thickness of double cream. Don't add the milk too fast as it will go lumpy, however you can switch to using balloon whisk after a while which will help get rid of any lumps. Take off the heat and add two thirds of the cheese, a heaped teaspoon of mustard, half teaspoon of salt, two pinches of white pepper and gently mix. If the cheese doesnt melt put the saucepan back on the heat for a few moments. Taste for seasoning.
Stir the pasta with a fork to seperate the individual pasta tubes and pour into the deep sided oven dish, pour over the cheese sauce and mix till evenly coated. top the mixture with the remaining cheese, then evenly distribute the sliced tomatoes. Season the top with a sprinkle of salt and a few grinds of black pepper.
Cook in the oven at 220° C, 200° C (fan) for 30-40 minutes, its ready when the top is golden brown and the sauce is bubbling round the edges.
This is good enough for a dinner party, served with a bowl of fresh green salad, balsamic vinegar dressing and some warm foccacia bread. Washed down with a deep red glass of wine.
Personally I cook this when I am unwell, I fill a big bowl full, smother it in tomato sauce and eat it in front of the telly, and always no matter how unwell I feel I always have seconds.
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