Black bean and sweet potato empanadas

Method

1. Heat the oven to 200°C/180°C fan/gas 6. Toss the sweet potato chunks, oil and ground coriander in a baking tray. Roast for 30 minutes until the sweet potato is tender, then add the black beans and chilli paste, toss to coat and roast for 5 minutes more.
2. Meanwhile, for the pastry, put the butter, salt, plain flour and paprika in a food processor and pulse until the mixture resembles fine breadcrumbs. With the motor running, pour in the warm milk until the mixture clumps together. (If you don’t have a food processor, rub the salt, flour and paprika into the butter in a large bowl using your fingers until it resembles crumbs. Work in the warm milk with a dinner knife until it clumps together.) Turn out onto a lightly floured surface and knead gently for a minute or so. Shape into a disc, wrap in cling film, then chill for 30 minutes.
3. Transfer the cooked sweet potato and beans to a bowl and mash with
   a fork. Mix in half the spring onions, season with salt and pepper, then cover and chill until completely cool.
4. Roll out the pastry on a lightly floured surface to the thickness of a £1 coin. (You might find the pastry easier to handle if you cut it in half before rolling.) Cut out about 20 x 7-8cm diameter circles using a ramekin or small bowl as a guide, re-rolling the pastry offcuts as necessary. Put around 1 tbsp of the chilled filling in the centre of each circle and brush the edges with water. Fold the pastry over the filling to enclose and squeeze the edges to close. Crimp the edges (like a Cornish pasty) to seal, or simply press with the tines of a fork.
5. Put the empanadas on 2 baking sheets lined with non-stick baking paper, then brush with the beaten egg yolk and milk mixture. Bake for 20-25 minutes until the pastry is golden and crisp.
6. To make the mayonnaise, put the saffron in a small heatproof bowl and pour over about 1 tsp boiling water. Leave for 5 minutes so the saffron releases its colour/aroma, then stir in the mayonnaise, lime zest and juice. Season to taste, then serve with the empanadas.