First, put some penne on to boil in plenty of salted boiling water. Cut streaky bacon into 3 cm chunks
and brown in a frying pan. Scoop out and set aside. Slice chestnut mushrooms and brown in olive oil
and butter. Scoop out and put with the bacon. Now add a Tbs plain flour to the oils in the pan
and cook for a couple of minutes, then add milk, stirring all the while, until you have a nice smooth sauce.
Stir in the bacon and mushrooms. When the penne is cooked, drain and add to the bacon and mushrooms,
together with a handful of grated parmesan and a few grinds of black pepper. Stir all this together
and tip into a greased casserole dish, sprinkle with more grated parmesan and bake in a 180°C oven
for 25 minutes, until bubbling and golden. Serve with a simple side salad.