1Place split peas into a large container and cover with 6 cups cool water; soak 8 hours to overnight. Drain and rinse.
2Mix chicken broth and 2 cups water together in a large pot over high heat; add ham, red onion, split peas, brown sugar, garlic, black pepper, and salt. Bring broth mixture to a boil, reduce heat, and simmer until peas are softened, about 2 hours.