Heat sunflower oil in a saucepan.

Add chopped onion and sauté until softened.

Add carom seeds, fennel seeds, and bay leaf to the saucepan and stir.

Add chopped sweet potato and radish to the saucepan and mix.

Pour in 1/2 cup of vegetable stock, add salt to taste, cover, and cook until the root vegetables soften.

Allow the mixture to cool slightly, then remove the bay leaf.

Puree the mixture in a blender until smooth.

Pour the pureed soup back into the saucepan.

Add bay leaf.

Adjust the consistency of the soup with additional vegetable stock, if needed.

Add black pepper powder and salt (if required) to taste.

Bring the soup to a boil.

Ladle the soup into serving bowls.

Stir in a tablespoon of hung curd or Greek yogurt into each bowl.

Garnish with chopped coriander leaves and radish strips.

Serve immediately.