Combine sauce ingredients except nuts in a pan, melt, boil for two minutes, and cool.
Cream 125g butter and 125g sugar until pale and fluffy using an electric mixer.
Beat in eggs gradually with one tablespoon of flour until the mixture is smooth.
Fold in the remaining flour and diced apples using a metal spoon.
Pour half the sauce and half the pecans into a buttered 1L basin, then add the sponge.
Cover the basin with a parchment disc and a pleated, buttered foil lid.
Place basin on a jar lid in a saucepan filled halfway with boiling water.
Cover saucepan and simmer for 2.5 hours until the sponge is golden and springy.
Invert pudding onto a plate and serve with remaining heated sauce and nuts.