To make the pastry, sift the flour together with a pinch of salt in a large bowl. Rub in the butter until you have a soft breadcrumb texture. Add enough cold water to make the crumb mixture come together to form a firm dough, and then rest it in the fridge for 30 minutes. Roll out the pastry on a light floured surface and line a 22cm well-buttered flan dish. Don’t cut off the edges of the pastry yet. Chill again. Remove the pastry case from the fridge and line the base of the pastry with baking parchment and then fill it with baking beans. Place on a baking tray and bake blind in the oven at 190`c for 20 minutes. Remove the beans and parchment and return to the oven for another five minutes to cook the base. Meanwhile, soften the onion and thyme together in a pan with the oil for a few minutes, then transfer into the pastry base, along with the cooked turkey pieces, Brie and dried cranberries. Combine the eggs with the milk and cream in a bowl and season well with salt and pepper. Pour the mixture over the pastry base and bake in the oven at 160`c for a further 30-40 minutes or until set.