Method

• To make the pastry, put the flour in a bowl, add the butter and rub together with your fingertips until the mixture resembles breadcrumbs
• Using a bread and butter knife in a cutting motion, combine the egg yolks with the mix until the pastry comes together, if it is a little crumbly add one teaspoon of cold water at a time until you get a firm, yet moist dough
• Turn out onto a lightly floured bench and quickly knead until the pastry is even and smooth, then wrap and place in the fridge to chill for at least 30 minutes
• While the pastry is resting make the filling
• Melt the butter with the oil in a large-heavy based pot or fry pan
• Add the finely sliced onion and cook over a low heat for 30 minutes
• Cooking the onions long and slow is essential as the natural sweetness comes out of them and the texture becomes soft and they almost melt together
• Cool slightly
• Heat the oven to 200C Roll out the pastry on a lightly floured surface and line a 30cm push up bottom flan tin or something similar, making sure there are no cracks
• Return to the fridge and rest for another 30 minutes, then line with baking paper and fill with baking beans
• Bake for 20 minutes, reduce the heat to 160C and cook for a further 15 minutes, or until the pastry is golden and set