1. In a bowl, mix the dry ingredients: ragi flour, all-purpose flour, cocoa powder, and salt, and keep aside.
2. Take a pan, add water to it, and place a bowl on top of the pan. Put the chocolate and butter into the bowl.
3. Melt using the double boiler method. Then slowly add sugar to it and mix well until the sugar melts completely.
4. In another bowl, beat the eggs until they are fluffy and airy.
5. Mix the dry ingredients and egg mixture into the chocolate-butter mix in three equal parts using the cut and fold method.
6. Add the vanilla essence and baking powder. Add the walnuts.
7. Grease the cake mold with butter and line it with baking paper. Pour the mixture into the mold, filling it two-thirds full. Tap the mold and garnish with walnuts on top.
8. Bake in a preheated oven at 180°C to 200°C for 30 to 35 minutes.
9.Remove from the oven and allow to cool. Unmold the brownie, remove the baking paper, and cut into pieces.
10. Serve hot with melted chocolate or vanilla ice cream.