Heat the oil in a frying pan over medium heat. Add the sliced leek and cook gently until soft and starting to caramalise, around 7-10 minutes. Set aside to cool.

Meanwhile, to a medium sixed bowl, add the eggs and cream and whisk until combined. Add in the peas, zest in the lemon and crumble in the ricotta in small to medium chunks. Add in the cooled leeks and season with salt and pepper.

Preheat the oven to 200C. Melt the butter and use a little of it to grease 4x10cm, loose-bottomed tart tins*. Place the tins onto a baking tray and set aside.

Working with 1 filo sheet at a time – while keeping the rest covered with a damp cloth – apply a light coating of butter to the whole sheet using a pastry brush. Fold the sheet in half so the butter is on the inside, and lightly butter only the top of the halved sheet before gently pressing it into the tart tin. Repeat with another sheet of filo pastry, this time adding it to the tart tin on an angle so you form a kind of cross shape.

Add spoonfuls of the filling mixture to the filo pastry-lined tart tin until just full. Next, gently scrunch up the pastry overhang to create a ruffled border, leaving the centre of the filling exposed. Repeat with the rest of the tart tins.

Butter the scrunched edges with the remaining butter and bake in the oven for 15 minutes or until the custard is set. Carefully and gently remove the tartlets from the tart tins before placing them onto the baking tray and back into the oven. Bake for a further 5-10 minutes or until the filo pastry is a crispy golden brown.

Serve hot as an elegant starter to dinner or at room temperature for a light lunch.