In a large pan, heat the cooking oil over medium-high heat.
Add the cumin seeds and cook for about 1 minute, until they begin to darken.
Add the garlic, and sauté for 3-4 minutes until browned.
Add the tomatoes and stir to combine, then add ginger, coriander, turmeric, salt, and cayenne. Sauté this mixture for 5 minutes, stirring frequently.
Add the water and mung beans. Increase the heat to high and bring the mixture to a boil, then reduce to low, cover, and simmer for 30 minutes, stirring the mixture once or twice.
Taste a few mung beans to make sure they are cooked. If they are, stir in the coconut milk, and increase the heat to medium-high.
Once the curry comes to the boil turn off the heat. Stir in the coriander and the juice of one lime. Taste and decide whether you'd like to add the second lime.
Serve and enjoy.
