• Preheat oven to 180°C (350°F).
• Line 33x23 cm (13x9 inch) baking pan with parchment paper( you can use a smaller pan, your squares will be taller than).
• Separate egg yolk from egg whites.
• In a large mixing bowl mix egg yolks, sugar, and vanilla extract until pale, pour oil and yogurt and mix until combined. Add flour and baking powder and mix until well incorporated.
• Beat egg white until soft peaks form. Carefully fold egg whites into the batter, and mix carefully with a spatula until mixture is incorporated.
• Pour mixture into prepared pan and bake 20-25 minutes until golden and a toothpick inserted in the center comes out clean.
• Leave the cake to cool to room temperature. When cooled, cut the cake into 5 cm (2.5 inches) squares.

Chocolate cream:

• In a medium saucepan melt butter and chocolate. Pour milk and add rum if using. Let it cook, and soon as it comes to boil, remove from heat. Leave it to slightly cool for a few minutes.

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• Put desiccated coconut in a deep plate.
• With the help of two forks, dip every square first into warm chocolate cream, drain the excess of cream, and roll into coconut.
• Store in an airtight container for up to 4 days.
• These freeze well.