For the cake mixture, I always make a very simple one that's so easy to remember. Equal quantities of butter, sugar and flour, half of that in eggs and another half in baking powder. So, for example, 4oz sugar, butter and flour, 2 eggs, 1tsp baking powder. Basically, mix it all together, I never bother creaming the butter and sugar first, but one tip I did learn was to just combine the flour at the end and mix as little as possible to prevent the gluten from stretching.
Basically, you make a toffee sauce, coat the softened chunks of apple in it (I chop mine and pop it in the microwave with a little sugar and water,) leaving some sauce to pour over the sponge at the end. Put a splodge of toffee covered apple in the bottom of a greased ramekin or dariole mould. Blob the cake mixture over the top and bake for between 10 and 20 mins. Tip out when cooked and pour over the sauce. It really was incredibly quick and easy, but absolutely delicious.