In a large bowl, combine the whole wheat flour, baking powder, baking soda, cinnamon, and nutmeg. You may sift these ingredients to ensure they are evenly distributed. Stir in the ginger paste and optional candied ginger or raisins. Mix well and set aside.

In a separate bowl, whisk the yogurt with ¼ cup of water until smooth and lump-free. Stir in the oil and mix thoroughly until well combined. Set this mixture aside as well.

Preheat your oven to 180°C (356°F) for at least 15 minutes, allowing it to reach the correct temperature for baking.

Heat ½ cup of water until it is just hot (no need to bring it to a boil), and add the jaggery. Stir continuously until the jaggery has fully dissolved. If there are impurities in the jaggery syrup, strain it through a fine mesh strainer to remove them.

Now, combine the yogurt-oil mixture with the dry flour mixture. Gently fold in the jaggery syrup and stir until you have a smooth, lump-free batter.

Grease a round or loaf baking pan and pour in the batter. Place the pan in your preheated oven and bake for 35 to 40 minutes at 180°C (356°F). Keep an eye on the cake – if the top starts to brown too quickly, cover it loosely with parchment paper or aluminum foil to prevent over-browning.

Test the cake’s doneness by inserting a bamboo skewer or toothpick into the center; it should come out clean when the cake is ready. Once done, remove the cake from the oven and allow it to cool completely in the pan on a wire rack.

Once fully cooled, carefully take the cake out of the pan. If desired, dust the top with icing sugar or confectioner's sugar for a decorative touch. Slice and serve as is or pair with a dollop of whipped cream for an indulgent treat.