prepare the coffee decoction by dissolving the coffee in lukewarm water. pour this in a flat dish (so its easy to dip the biscuits in). set aside.
dissolve the custard powder in 2 tablespoons of milk. set aside.
boil the rest of the milk with the sugar. when the milk is just boiled, turn off the heat and add the custard mixture, stirring well. set aside to cool slightly.
dip the savoiardi biscuits (sugar side down) in the coffee decoction for about 2 seconds each, and layer them in a dish with dipped face up. this helps the coffee seep through the whole biscuit and soak it evenly.
pour half the custard over the biscuit layer, spreading it evenly. place the dish in the fridge to set the custard.
dissolve the cocoa powder in a 2 tablespoons lukewarm water and add it to the remaining half of the custard. mix well, and put it back on a gentle heat so that the cocoa assimilates fully into the custard. set aside to cool slightly.
as the chocolate custard is cooling, remove the dish from the fridge and prepare a second layer of coffee soaked savoiardi biscuits on top of the first layer.
pour the chocolate custard over the second layer of biscuits and make sure it is spread evenly.
while the custard is still warm on top, garnish with the white chocolate chips, butterscotch chips and slivered almonds.
cover the dish in cling and let it rest in the fridge to set the custard layers fully (can be done upto a day ahead, but at least 2 hours).