Preheat oven to 180°C (350°F).

Melt butter in a saucepan over low heat, ensuring it doesn't boil.

Sieve cocoa powder into the melted butter and stir until smooth.

Remove from heat and add vanilla extract.

Add brown sugar and stir well until slightly melted.

Sieve ragi flour, wheat flour (or maida), and baking powder into the mixture and combine well.

Whisk eggs well using a hand mixer and add them to the mixture.

Stir in almonds or walnuts (if using) and mix well.

Add milk for a smoother texture.

Pour the batter into a greased baking tin and bake for about 25 minutes, or until a tester inserted in the center comes out clean.

Let cool completely before cutting into squares and serving.

Store in an air-tight container in the refrigerator for up to 3-4 days.