In a large frying pan, melt the butter over a medium heat.
Once it stops bubbling, add the 16 leek lengths, lemon zest, and juice.
Season well with salt and pepper.
Cook the leeks gently for 12-15 minutes, turning them every 3 minutes to ensure they cook evenly. They should be soft enough to be easily pierced with a knife.
Set aside in the pan with their buttery juices.
Preheat your oven to 180°C (350°F) / 160°C Fan / Gas Mark 4. On a lightly floured surface, roll out the puff pastry to a rectangle of about 30 x 20cm.
Slice the pastry into four equal smaller rectangles. A pizza cutter works perfectly for this.
On a baking tray, arrange four sets of four leek lengths, creating four leek 'rectangles' slightly smaller than your pastry pieces.
Spoon 1 tbsp (15 ml) of the buttery lemon juices over each leek pile and sprinkle with most of the toasted pine nuts, reserving some for garnish.
Carefully lay a pastry rectangle over each pile of leeks, ensuring it covers them completely. Press the leeks closer together if needed.
Bake for 10-12 minutes, or until the pastry is golden brown and well-risen.
While the tarts bake, prepare the greens.
Discard any remaining liquid from the leek pan but do not wash it.
Add the sunflower oil and heat.
Add the wild garlic and a pinch of salt. It will look like a lot, but it will wilt down in a minute or two.
Turn it constantly to cook evenly. (If using the substitute, sauté the chopped garlic for one minute before adding the spinach and wilting).
To serve, let the tarts cool for a moment. Slide a spatula or fish slice under one tart, and carefully flip it over onto a plate so the pastry is now the base.
Garnish with the remaining pine nuts and serve the wilted greens on top or alongside.
Don't chop your leeks into small discs.
Keeping them in long lengths helps them hold their shape beautifully during cooking.
Don't wash the leek pan before wilting the greens. The leftover buttery, lemony juices add a fantastic layer of extra flavour.
