Heat the oil in a roomy pot over medium heat. Add the onion and garlic. Sauté, stirring occasionally, for 5 minutes, or until the onion is soft and clear.
Add the water, potatoes, lentils, curry, turmeric, ginger, and salt. Bring the mixture to a boil. Reduce the heat to low, cover, and simmer for 30-40 minutes, or until the lentils are cooked through.
Add the peas and spinach. Cook for another 5 minutes. Stir in the cashew cream or coconut milk and lime. Taste the stew and adjust salt and lime as needed. Serve.
Notes
You can substitute 1/4 cup broth or water for the oil if you like.