1. For the pastry, put the flour, caster sugar and icing sugar into a bowl. Rub in the butter until the mixture resembles breadcrumbs.

2. Beat the egg yolk with the water and add to the flour mixture. Mix and knead gently to form a soft dough.

3. Wrap in cling film and chill for 30 minutes. Roll out the pastry and use to line four 4 inch fluted tart tins.

4. Line with parchment, fill with baking beans and bake blind in a hot oven set at 190°c / 375°c / Gas Mark 5 for 15 - 20 minutes.

5. Allow the cases to cool. Put the rhubarb and cordial in a pan and heat gently, covered until the fruit is soft but still holding its shape.

6. Gently turn the fruit in the pan juices and taste for sweetness. If too tart for your taste, add the caster sugar. Let the fruit cool.

Crumble

7. Rub the butter into the flour until the mixture resembles rough breadcrumbs.

8. Stir in the oats and caster sugar.

9. Once again, turn the fruit in the pan juices and spoon into the pastry cases. Top with the crumble topping and return to the oven for 15 minutes.

10. Serve warm with cream, custard or ice cream.