Step #1 Preheat oven to 200 degrees Celsius
Melt 1 oz of the butter in a frying pan & fry the onion, & courgettes for 5-7 mins, peppers, garlic, until soft.
Step #2 Meanwhile, parboil the potatoes in boiling salted water for 5 mins.
Step #3 Drain & cool by rinsing in cold water.
Step #4 Layer half the potatoes over the base of a 3pt oven proof dish.
Step #5 Spoon over the pepper mixture then the rest of the potatoes.
Step #6 Place the remaining butter, & milk in a saucepan & cook over a low heat, whisking, flour, until it boils & thickens.
Step #7 Stir in the cream & pour the sauce over the potatoes.
Step #8 Scatter over the cheese & thyme leaves & season this with salt & freshly ground pepper.