- Preheat the oven to 200˚C/Fan 180˚C/Gas 6.
- Peel the potatoes and chop them into 2cm chunks, parboil the potatoes until the tip of a small, sharp knife almost reaches to the centre of the potato, drain and leave in the colander to allow the steam to dry off the potatoes.
- Blanch the leeks in a pan of boiling, salted water for 3-4 minutes until slightly softened, drain and add to the potatoes.
- Now to make the sauce, in a pan melt the butter, add the flour and cook until the flour is golden and has the consistency of wet sand. Add the milk in stages, whisking away all the lumps before adding more. Reducing the heat to a minimum will help.
- Once all the milk is in, add the bay leaf, thyme and nutmeg. Whisk in the grated goat's cheese. Add more seasoning if required.
- Fold the potatoes and leeks into the sauce, and pour into a suitable pie dish.
- Lay out a sheet of filo, brush the surface with the melted butter then sprinkle with sea salt and a few twists of black pepper.
- Roughly crinkle up the pastry, a bit like a scrunched-up paper ball and place on top of the filling, now make some more until the whole of the pie is covered.
- Place into a hot oven, 175ºc for 20-25 mins or until the filo is beautifully crispy and golden, with bubbling sauce creeping out from underneath. Serve with some simple buttered greens.