50 g butter
2-3 onions, large (about 600 g), sliced
150 ml thickened cream
100 g gruyère, grated
200 g plain flour
100 g unsalted butter
2 tsp thyme leaves
- To make the pastry, pulse the flour, butter, thyme and ½ tsp salt in a food processor until the mixture looks like breadcrumbs.
- Tip into a bowl then gradually add iced water, stirring with a knife, until it comes together. Wrap in clingfilm and chill for 30 minutes. Heat the oven to 190C/fan 170C.
- Roll out the pastry to the thickness of a $1 piece on a lightly floured surface.
- Carefully use it to line a shallow 23cm tart tin. Leave the excess pastry overhanging.
- Sit the tart tin on a baking sheet. Line the pastry with baking paper and fill with baking beans. Bake for 15 minutes, then remove the beans and paper, and cook for another 5-10 minutes until there are no raw patches. Leave to cool for five minutes.
- Trim off the excess pastry while it is still warm with a small serrated knife.
- Melt the butter in a large pan. Add the onions and cook over a low heat, stirring occasionally, until they’re golden and meltingly soft (this will take about 20-30 minutes, so be patient).
- Whisk the cream, eggs and cheese, and season well. Arrange the onions in the pastry case then pour over the egg mix. Slide the case back in the oven for 15-20 minutes or until the filling is just set. Serve warm.