Combine lentils in a heavy pot with 5 cups of water. Bring to a boil and remove any surface scum. Add the turmeric powder and ginger.
Cover, by leaving the lid slightly open, turn heat to low, and simmer gently for 1 1/2 hours or until the lentils are tender.
Stir every 5 minutes or so during the last half hour of cooking to prevent it from sticking to the bottom of pan. Remove ginger slices. Add salt and garam masala and stir to mix.
Heat the oil in a small frying pan over medium heat. When it is hot, add the cumin seeds and garlic.
Stir and fry until the garlic pieces are lightly brown. Add the red chilli powder into the pan. Immediately lift the pan off the heat and pour the entire content (oil and spices) into the pot with the lentils. Stir to mix.