Heat the oil in a large saucepan over medium-high heat. Add onion; sauté 3 minutes or until tender. Stir in curry paste; cook 1 minute. Add 1/2 cup broth, carrot, ginger, red pepper, and garlic; cook 6 minutes or until carrot is tender, stirring occasionally. Add 3 1/2 cups broth, lentils, and soybeans; bring to a boil. Reduce heat; simmer 10 minutes or until lentils are tender. Stir in cilantro, salt, and black pepper. Divide evenly among 6 bowls; dollop with yogurt. Garnish with cilantro sprigs, if desired.