Combine first 4 ingredients in a large saucepan; bring to a boil. Reduce heat, and simmer 20 minutes. Spoon into a bowl; cool to room temperature. Discard bay leaves.
While tomato mixture cools, heat oil in a small nonstick skillet over medium heat. Add mustard seeds and red chiles. Cook, partially covered, 3 minutes or until seeds begin to pop, shaking pan frequently. Cool and discard red chiles. Add mustard mixture, coconut, and serrano to tomato mixture. Stir in yogurt. Serve immediately.