Place them in a deep pot, add the water, turmeric, and salt, and bring to a boil. Boil the peas gently, partially covered, until they are very soft, about 45 minutes, checking and stirring occasionally to ensure they do not stick to bottom of the pan.
Turn off the heat and beat the split peas with a wire whisk or wooden spoon for a minute or until they look thick and creamy.
You should have 5 cups of puree; if not, add additional water.
Return the puree to the pot, add black pepper, and heat until boiling.
Turn off the heat and fold in the chopped coriander; keep the dal covered.
Heat the oil in a frying pan over medium heat. When the oil is hot, add the cumin seeds.
When the seeds turn several shades darker, add the garlic and optional red peppers. Cook until the garlic is browned and the oil is infused with its flavor.
Pour the oil-garlic mixture onto the dal. Mix well.