My original idea was to make a Potato Cake. But during the process, the required sponginess was not obtained. So I altered the recipe into a crispy one.
The cocoa filling adds an extra flavour to the potato cake.
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Ingredients:
Potato (boiled) – 5
(Approximately 1 cup, when mashed)
All purpose Flour / Maida – ½ cup
Sugar – ¾ cup
Egg – 2
Vanilla essence – ½ tsp
Baking powder – ¼ tsp
Chocolate bar – 1
(Approximately 50 gms)
Salt – ¼ tsp
Cocoa Filling:
Icing sugar – 2 tbsp
Cocoa powder - ½ tbsp
Fresh cream – 1 tbsp
Preparation:
Grind the potatoes into a fine paste.
Sift the flour and baking powder.
Beat the eggs till it becomes little fluffy.
In a bowl, mix the potato paste, flour, sugar and eggs without any lumps.
Break the chocolate bar into small pieces (chips).
Add vanilla essence & chocolate chips to the cake mixture and mix well.
Grease the baking pan with butter or oil & dust with flour.
Pour the mixture and bake for 30 minutes at 180° C (356 F).
Let it cool for sometime and cut the cake into small rectangular pieces.
Broil them for 20 minutes at 180° C.
(As I have a mini oven, I broiled each side separately for 15 minutes.)
Mix icing sugar, cocoa & fresh cream and keep stirring in a low flame till it becomes a thick paste.
Spread the cocoa paste on one piece and press it with the other one. Likewise do for all the pieces.
Bake them for 3 minutes at the same temperature.
Serve for a dessert after lunch or dinner.

Note:
I actually added 7 potatoes and it came out as a pancake (like maida dosa). So I reduced the number of potatoes to 5 in this recipe.