For the pastry, mix the butter and sugar together with a wooden spoon until softened. Add the flour and baking powder and mix with your fingers until damp and sandy. Add the egg and knead very gently so that the pastry comes together. Flatten a little and wrap in plastic. Refrigerate for 1 hour before rolling out. Preheat your oven to Gas 4, 180°C, fan160°C.
Roll out the pastry on a floured work surface to line a 26cm (10½in) tart tin with sides at least 3cm (1¼in) high. Line with baking paper, fill with baking beans or weights and blind bake for 20 minutes. Remove the beans and paper when the visible pastry is golden. Prick the pastry base a few times with a fork and bake for a further 10 minutes to dry out the bottom.
To make the filling, put the milk and butter in a pan over medium heat to melt the butter. Whisk the egg yolks with the sugar and vanilla, then whisk in the cornflour. Add a ladleful of the hot milk to the eggs, whisking to avoid scrambling them. Mix it all together well and leave to cool.
Whisk the egg whites to soft peaks then gradually fold into the filling. Pour into the tart case, sprinkle the sugar and cinnamon over the top and return to the oven for 30 minutes, or until it is set and just a bit wobbly. Cool before serving.
Tip: You might like to make double the pastry and freeze it ready rolled-out in the tin so that you can whip it straight into the oven whenever you need to produce a pudding in a rush.
Falling Cloudberries: A World Of Family Recipes by Tessa Kiros, published by Murdoch Books, £17·99. Click here to buy the book.
See more Baking recipes