Ingredients
- 1¼ cups (155 g/5 oz) plain flour
- 155 g (5 oz) chilled butter, chopped
- 3–4 teaspoons iced water
Filling
- 1 kg (2 lb) brown onions
- 45 g (1½ oz) butter
- 1 tablespoon olive oil
- 3 teaspoons plain flour
- 3 eggs
- ¾ cup (185 ml/6 fl oz) cream
- 2 tablespoons milk
- pinch of nutmeg
- 60 g (2 oz) Gruyère or Swiss cheese, grated
Method
1. Sift the flour into a large bowl and add the chopped butter. Using your fingertips, rub the butter into the flour until the mixture resembles fine breadcrumbs. Add almost all of the water and use a knife to mix it to a firm dough, adding more water if necessary. Turn the dough out onto a lightly floured surface and gather it together into a ball. (The pastry can also be made in a food processor.)
2. Wrap the pastry ball in plastic wrap and refrigerate for about 20 minutes. Working quickly, press the chilled pastry into a 26 cm (10½ inch) fluted flan tin. Refrigerate the shell for 15 minutes, or until firm. Preheat the oven to moderate 180°C (350°F/Gas 4). Place a sheet of baking paper over the pastry and fill with dried beans or rice. Bake for 10 minutes. Remove the paper and the beans or rice, and bake the shell for a further 5 minutes, or until the pastry is almost cooked. Allow the shell to cool.
3. To make Filling: Slice the onions into rings. Heat the butter and oil in a large heavy-based pan. Add the onion rings and cook over low heat, stirring occasionally, for 30–35 minutes, or until they are very tender and golden. Sprinkle with the flour and cook, stirring, for 2–3 minutes, or until the mixture is golden. Remove from the heat and allow to cool completely.
4. Beat the eggs, cream, milk and nutmeg together in a large bowl. Gradually stir in the cooled onion and half the grated cheese. Spoon into the pastry base, sprinkle with the remaining cheese and bake for 20–25 minutes, or until the tart is golden and cooked through. Set aside for 10 minutes before serving.
