Greek-style potato, courgette and feta bake

I bought a kilo of courgettes at the weekend and, thinking of different ways to use them, remembered this easy Greek-style bake I invented a couple of years ago. I only had salad potatoes (Anyas) whereas I'd normally use a bigger waxy potato like a Desirée but they worked perfectly well.

Serves 3/4
4 medium sized potatoes (about 600g), peeled
Half a bunch of spring onions (about 4) or 1 medium onion, peeled and finely sliced
2 medium to large courgettes (salted if large*)
200g feta cheese
4 sprigs of mint
2 tbsp olive oil
300ml vegetable stock made with 1 rounded tsp vegetable bouillon powder or 1/2 a vegetable stock cube
Freshly ground black pepper

Preheat the oven to 190°C/375°F/Gas 5. Trim the roots and the top half of the green leaves off the spring onions. Cut them lengthways into quarters then across into three. Halve and finely slice the potatoes. Cut the ends off each courgette and slice the rest finely. Pull the leaves off the mint and chop roughly. Pour 1 tbsp of olive oil into a large baking dish and smear it round the base and sides of the dish. Put a layer of potatoes over the bottom of the dish (about one third of the sliced potato) top with half the onions, half the sliced courgettes and half the feta, evenly crumbled over the courgettes. Scatter over half the mint and season with freshly ground black pepper. Repeat with another layer of potato, onion, courgette, feta and mint then finish with a layer of potato. Pour the stock over the vegetables then trickle the remaining olive oil over the top of the dish. Bake for an hour to an hour and a quarter or until the potatoes are completely tender (you should be able to stick a knife through them easily) and the top is brown and crispy. (About half way through the cooking time tilt the pan and spoon a little of the juices over the potatoes.) Nice on its own but even better with a tomato salad.

* If the courgettes are rather large and threaten to be watery I'd salt them lightly and leave them to drain half an hour. Rinse and pat them dry before using them.