275g golden caster sugar
2 tsp lemon juice
6 egg yolks
250g salted butter, softened
225g plain flour
icing sugar, to dust
1. Line the base of a 23cm springform cake tin with baking parchment. Put the blackberries in a small saucepan with 25g caster sugar and 4 tbsp water. Set over a medium heat and bring to the boil. Simmer gently, crushing the berries with the back of a wooden spoon, for 6-8 minutes, until thick and jammy. Add the lemon juice and set aside to cool.
2. Mix the egg yolks in a small bowl, then transfer 1 tsp to another bowl; stir in 1 tbsp water to make a glaze and set aside. In a large bowl, combine the remaining 250g sugar and the butter with a wooden spoon. Add the flour and roughly combine, then mix in the egg yolks to make a smooth but sticky dough. Cover and chill for 20 minutes.
3. Preheat the oven to 180˚C, gas mark 4. With a floured spoon, drop tablespoons of ½ the dough over the base of the parchment-lined cake tin. With floured fingers, spread it out in the tin and pat down well. Smooth over the cooled blackberry mixture, then carefully top with the remaining dough, using a palette knife to smooth the surface. Brush with the egg yolk glaze, then score diagonal lines across it to make a diamond pattern.
4. Bake for 40 minutes, covering the top loosely with foil if it colours too much. Leave to cool in the tin before running a knife around the edge and removing. Dust with icing sugar and slice into wedges to serve with cream, if liked.
This recipe first appeared in Waitrose Food, August 2017 issue. Download the Waitrose Food app for the full issue
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