Generously butter a small glass bowl and place the chopped fudge into the base.
Place the sugar and butter in a separate bowl and beat until light and fluffy.
Place the powdered egg into a bowl with a splash of water and mix until smooth, then add to the sugar and butter mix.
Add the flour, fizzy water and one tablespoon of the condensed milk, stir well to mix and pour into the bowl with the fudge. Place into the microwave and cook on high power for six minutes and then turn out onto a plate.
To serve, drizzle the toffee pudding with the remaining tablespoon of condensed milk.