In a food processor combine the flour and butter and pulse adding the egg yolk and water gradually until the pastry comes together in a ball. Remove from the food processor, wrap in cling film and chill in the fridge for 30 minutes.
Preheat the oven to 180 C / Gas 4. Grease and line a quiche dish or tart tin.
Turn the pastry out onto a lightly floured work surface and roll out to a thickness of about 5mm. Transfer to the prepared quiche dish or tart tin and gently press into the base and sides to line. Brush with reserved egg white.
Bake in the preheated oven for 6 to 8 minutes or until blushing golden brown. Remove from the oven and leave it to cool.
For the filling:
Warm the oil in a frying pan over a medium heat. Add the spring onions and brown, cut side down. Remove and allow to cool.
Into the same frying pan, add the garlic, spinach and mint, wilt it then remove from the heat and allow it to cool.
Put ricotta, eggs and Parmesan cheese in food processor and whiz until it is smooth. Stir the ricotta mix through the spinach mix, salt and pepper to taste and spoon it into the prepared pastry case. Place the onions on top, cut side up, pressing them into the mix.
Bake in the preheated oven until the pastry is golden brown and the filling is firm to the touch, 35 to 40 minutes. Remove from the oven and serve warm or allow to cool before serving.