How to Make It
In a large pot, heat the oil over moderately low heat. Add the onion, garlic, cumin, mustard, coriander, cayenne, cloves, and ginger and cook, stirring occasionally, until the onion is translucent, about 5 minutes. Stir in the tomatoes and cook for 5 minutes more.
Add the split peas, water, salt, and chicken breasts to the pot. Simmer, partially covered, until the chicken is just done, about 10 minutes. Remove the chicken breasts with a slotted spoon.
Continue simmering the soup, partially covered, stirring occasionally, until the split peas are tender, about 20 minutes. Shred the chicken and return it to the soup along with the black pepper. Serve the soup topped with cilantro leaves, if using.
Indian cooks prefer to use whole spices and grind them as needed. Commercially ground spices may not be quite the same, but they are quicker. Just remember that they do lose strength over time and are best used within a year of their purchase.