Boil the potato slices in salted water until almost cooked, drain them and set aside.
Melt half of the butter in a frying pan with the garlic, and half of the courgette slices, sprinkle with half of the mixed herbs. Fry till just golden on both sides, set aside. Cook the remaining courgette slices in the same way. set aside.
Grease a low sided oven dish with the extra butter.
Layer the potatoes and courgette in the dish so that they over lap like roof tiles.
Whisk the egg with the cream and milk, season with pepper and salt, pour into the dish to cover the potatoes and courgettes.
Grate the cheese and sprinkle over the dish.
Place in hot oven 200c till brown aprox. 20 minutes.