Why Nicky? No one seems very sure, although it could be because traditionally this northern sweet treat was covered with a single sheet of pastry cut with little ‘nicks’ to let the steam escape.
For the filling, mix the dates, apricots, ginger, rum and sugar together in a bowl. Set aside to soak while you make the pastry.
For the shortcrust, mix the flour and icing sugar together in a bowl. Add the diced butter and rub in with your fingertips until the mixture resembles fine breadcrumbs.
Mix the egg with the lemon juice and water. Make a well in the centre of the flour mixture and pour in the egg mixture.
Using one hand, work the liquid into the flour to bring the pastry together. When the dough begins to stick together, gently knead into a ball. Wrap the pastry in baking paper and chill it for at least 15 minutes.
Heat the oven to 180°C/160°C fan/350°F/Gas 4. Cut the dough into 2 pieces, roughly one third and two thirds. Roll out the largest piece on a lightly floured surface and use it to line the pie dish, leaving the excess hanging over the sides.
Spread the filling in the pastry case and dot with the butter.
Roll out the remaining pastry and cut into 14 long strips about 1cm wide. On the lined pastry board, use the pastry strips to create a lattice with 7 strips going each way, passing them under and over each other.
Dampen the rim of the pastry in the tin with water, then invert the lattice from the paper onto the tart. Press the ends of the lattice strips to the pastry rim to secure, then crimp the edges. Trim, then brush the lattice with the beaten egg.
Bake for 15 minutes, then turn down the oven to 160°C/140°C fan/315°F/Gas 2–3 and bake for a further 20 minutes, until the pastry is golden.
For the rum butter, beat together the butter and sugar, then gradually beat in the rum. Serve the tart warm or cold, with a spoonful of butter for each serving.