Eggless banana chocolate cake (cooked in a microwave)

In all these years that we have been married, I've never baked my husband a birthday cake- he doesn't have egg yolk, and the only cakes I know are "contaminated" with eggs. 
But this is his 40th birthday, and I thought it was high time I took the plunge. Since nobody I knew seemed to have a good recipe for eggless cake, I took to google, and found this recipe where bananas were substituted for eggs. The results were better than expected, though I would have preferred the cake to have risen a bit more.

You need
Flour/ maida- 1 cup
Sugar - 1 cup
Milk- 1 1/2 cup
Cooking oil- 3/4 cup
Ripe banana- 1, mashed
Cocoa powder- 1 1/2 tbsp
Baking powder - 1 tsp

1. Sieve maida, baking powder and cocoa powder two or three times (Mother's baking tip- the more you sieve, the lighter the cake will be)

2. Warm the milk, and mix the mashed banana in it. Add oil and sugar, and stir till sugar dissolves.

3. Add the maida+cocoa powder+ baking powder mixture one spoonful at a time, making sure it mixes well. Stir in one direction only.

4. At this stage, I added half a coarsely mashed banana to give texture- you can skip it.

5. Pour into a pre-greased baking dish and bake at recommended settings (I required 5 minutes). Test by pushing in a toothpick- if it comes out clean, it is done.

6. Allow to cool. The next step is optional.

7. Cut the cake in half, if rectangular, or bake two identical cakes using the same amount of batter. Spread a thin layer of Nutella on half the cake, arrange thinly sliced bananas in a layer, and place the other half over it, pressing slightly.

I loved the combination of banana and chocolate, but can also add texture by adding walnuts instead of, or in addition to the cocoa powder.