Step 1

In a large, heavy pot, heat fat on high, then add onions. Cook until soft and slightly browned, 10 to 15 minutes, then add ginger, chiles, and spices. Stir constantly to prevent spices from sticking and burning.

Step 2

When mustard seeds start to pop, add lentils and 6 cups water. Bring to a boil, then reduce to a simmer and cook, covered, until lentils almost completely fall apart, about 1 hour. Stir occasionally to prevent sticking and add water as needed. When lentils are soft, add salt to taste.

Step 3

Ten minutes before serving, stir in vadouvan. Serve warm with yogurt and cilantro, if desired.