Heat oil in a heavy bottom pot over medium heat. Add onions and sauté until translucent and fragrant, about 7 minutes. Add garlic and ginger and cook for one more minute. Stir in curry powder.
Add vegetable broth or water and split peas. Bring to a boil then reduce heat to a simmer. Cover and simmer for 10 minutes. Add sweet potatoes and continue to simmer for another 30 minutes, stirring occasionally, until the split peas are cooked all the way through.