Rinse and pat dry the karelas, then slit each lengthwise and scoop out the seeds and pith.

Bring a pot of lightly salted water to a boil. Add the prepared karelas and simmer for 10 minutes, then drain and set aside.

In a skillet over medium heat, warm 1 tbsp of oil. Add the diced onions and sauté.

Stir in the turmeric, red chilli powder, garam masala, and amchur. Add the mashed potato and cooked chana dal, and season with salt. Cook, stirring, until the mixture is dry and holds together.

Fill each karela with the potato-dal filling. If needed, tie them gently with kitchen twine to keep the stuffing inside.

In the same skillet, heat the remaining 2 tbsp oil. Fry the stuffed karelas on all sides over medium heat until crisp and golden brown, about 8 to 10 minutes total.

Transfer to a serving platter and sprinkle with chopped coriander leaves.