Make the pastry. Sieve the plain flour and icing sugar into a mixing bowl, then cut the butter into small cubes and either use your fingertips to rub it into a breadcrumb-like texture or use a K-beater. Once the texture has been achieved, add the egg and work the mix until it forms a ball. If extra liquid is needed, add a splash of milk.
Dust a work surface with plain flour and roll out the pastry. Next, press the pastry into a greased tart case and refrigerate. (Optional: blind bake before continuing with the steps below).
Meanwhile, peel and core the apples, then cut them into rough chunks. Put them in a saucepan with half the lemon juice, a splash of water and sugar. Cook at a low temperature until the apples breakdown and fall apart at the touch of a fork. Beat the apples into a thick compote and season with the cinnamon.
Mix the allspice into the mincemeat, and then spread it over the base of the tart. Top with the apple compote. Finally, put the remaining lemon juice in a bowl and cut the eating apple into slivers – putting them in the bowl as you go, so they get a light coating with lemon juice to stop them from browning. Arrange the apple slices in a cartwheel on the top of the tart, and bake for 25 minutes at 180C.