Step 1

Boil the kettle and set a very large, deep, frying pan over a high heat. Put a splash of boiling water in the pan, then add as much spinach as will fit and cook until wilted, using tongs to stir it around. Tip it into a colander in the sink and repeat with the remainder and another splash of water. Once all the spinach is in the colander, press down with a plate to squeeze out as much water as you can. Remove and lay the spinach on kitchen paper in a single layer. Cover with more kitchen paper and press down. Leave to dry while you continue with the recipe (see tip).

Step 2

Meanwhile, over a low-medium heat, soften the leeks, onion and garlic in a frying pan in a drizzle of olive oil for 12 minutes. Transfer to a plate and leave to cool.

Step 3

Mix the cheeses, herbs, chilli flakes (if using), eggs, spring onions, zest, nutmeg and the onion mixture in a medium bowl. Give the spinach one last squeeze, then chop, add to the bowl and mix well. Season well. Heat the oven to 200°C/180°C fan/gas 6 with a baking sheet inside.

Step 4

Unroll the filo pastry on a clean work surface and cover with a slightly damp tea towel. Put the 50ml olive oil into a bowl and, using a pastry brush, lightly brush the 30cm loose-bottomed tart/cake tin with oil. Lay one sheet of filo lengthways so its centre is on the edge of the tin, with half the sheet in the tin and half overhanging. Brush the filo sheet lightly with oil, then lay another sheet next to it, partially overlapping the first sheet but a little further around the tin, again overhanging. Brush with oil. Continue with all 6 sheets of filo – like the spokes in a wheel – brushing lightly with oil as you go until the tin is fully lined.

Step 5

Spoon in the filling, then fold over the hanging filo sheets in the reverse order you laid them, brushing the tops lightly with oil. Sprinkle with sea salt and black sesame seeds. Bake for 35-40 minutes until crisp, covering with foil if it’s browning too much. Leave to cool slightly, then serve warm or at room temperature.