Combine the flour, brown sugar, cinnamon, nutmeg, coconut, sultanas and chopped walnuts in a large bowl. Make a well in the centre.
In a large jug, whisk together the applesauce, milk, butter, vanilla and egg. Using a wooden spoon, stir the wet ingredients into the dry ingredients to form the pudding batter. Spoon the pudding batter into your Russell Hobbs Pressure Cooker bowl and smooth it to the edges with a wooden spoon.
Meanwhile, peel, core and quarter the apple. Slice each quarter thinly to produce thin wedges to place on top of the pudding batter. Gently press on each slice to sit in the batter – this will give you a lovely texture on top of the pudding when it’s cooked.
Crumble the brown sugar over the top of the batter and then gently pour the boiling water over the top. Secure the lid in place (do not stir).
Press the PUDDING function and adjust to LESS. When it has finished the cooking cycle, release the pressure manually using the quick pressure release method.
Let the pudding rest for 5 minutes with the lid off. Serve warm using a silicone spoon or wooden spoon, making sure to scoop up the sticky sauce from the bottom.