Lightly grease a 23cm loose-bottomed, fluted flan tin with a pastry brush. Lightly dust a clean work surface with the flour and tip the pastry out onto it. Roll out the pastry into a circle that’s bigger than the flan tin. Gently lay the pastry into the tin and press carefully into the base and sides. Leave any overhang over the sides of the tin. Chill in the fridge for 30 mins.

Meanwhile, heat the oil in a frying pan over a low-medium heat. Stir in the onion with a large pinch of salt and fry gently for 15 mins until beginning to soften. Tip in the spring onions and cook for a few mins until slightly softened. Transfer to a plate and leave to cool slightly.

Heat the oven to 200C/180C fan/gas 6. Scrunch up a sheet of baking parchment and line the tin, ensuring it goes over the edges. Fill with baking beans, all the way up the sides of the tin. Bake for 15-20 mins. Remove the beans and parchment and bake for a further 5-10 mins until lightly golden and sandy to the touch. If the pastry has puffed up, gently press it down using a cold, metal spoon. Once cooled slightly, trim the pastry edges.

While the pastry is baking, whisk together the eggs, egg yolk, milk and chives in a jug. Season well with salt and black pepper.

Reduce the oven temperature to 180C/160C fan/gas 4. Place the flan tin on a baking sheet and scatter the onions evenly over the base. Sprinkle over most of the grated cheddar and pour over the egg mixture. Top with the remainder of the cheese and bake for 25-30 mins, until set and lightly golden; the middle should have a very slight jiggle. Remove and allow to cool for 10-15 mins before slicing. Serve warm along with a crispy green salad, if you like.