Bring together the thinly sliced potatoes, aubergine and fennel in a large pan of boiling water. Cover the pan, bring back to the boil and simmer for 4 minutes.
Now, add in the courgettes and simmer for a further minute – drain well.
Take a pan, heat some oil and lightly cook the onion and garlic. With the onion and garlic softening, place the Welsh Beef mince into the pan and leave to cook for about 3-4 minutes – until brown all over.
Leave the vegetables to one side, place the remaining ingredients into the pan with the Welsh Beef, bring to the boil and simmer for 10 minutes with the lid off.
Remember to remove the bay leaf. Take a family sized gratin dish and place a layer of mince on the bottom of the dish. Follow with a layer of sliced vegetables and repeat using all the mixture – finishing with a layer of vegetables.
With the layering complete mix together the egg, yoghurt and milk and spoon onto the top of the mixture – smooth evenly to cover the dish.
Finally, pour the yogurt mixture over the last layer of vegetables and sprinkle with the cheeses.
Bake in a preheated oven for 35-40 minutes until the topping is golden and serve with a delicious seasonal mixed salad.