Ultimate pissaladière

Method

1. For the pastry, tip the flour onto a clean work surface or into a mixing bowl and sprinkle over a pinch of salt. Add the butter, toss so all the pieces are coated, then rub the butter into the flour using your fingertips until the mixture has the consistency of very coarse breadcrumbs (it should look rather pebbly). Sprinkle over the water and bring the flour and butter together with your hands until there are no dry crumbs left. Flatten into a rough circle, wrap well, then chill for around 30 minutes.
2. Heat the oven to 180°C/160°C fan/gas 4. Warm the olive oil in a large frying pan over a low-medium heat. Add the onions with a small pinch of salt and cook, stirring occasionally, for 30-35 minutes until they’re soft and gently caramelised. Season to taste (but don’t over-salt, as you want them to remain sweet as a contrast to the olives and anchovies) and set aside to cool (see Make Ahead).
3. On a lightly floured work surface, roll out the pastry to a 28cm round that’s about 2mm thick. Drape the pastry onto the prepared tray, spread over the cooled onion mixture, then top with the anchovies and olives. Fold in the overhanging pastry edge to create a border, crimping as you go. Whisk 1 tsp water into the egg. Brush the edge of the pissaladière with the egg wash, then bake for 40 minutes or until the pastry is golden.
4. Remove the pissaladière from the oven and allow to cool slightly before serving – alternatively, it’s equally delicious served at room temperature.