Heat a large skillet over medium heat; add rice and lentils. Cook and stir until toasted and fragrant, 3 to 4 minutes. Rinse.
Place rice-lentil mixture, 1 tablespoon ghee, and salt in a rice cooker or pressure cooker; add water. Cook according to manufacturer's instructions until rice and lentils are tender and the consistency of a paste, 20 to 25 minutes. Stir and mash into a fine paste.
Heat 1 tablespoon ghee in a skillet over medium-high heat. Add black pepper and cumin seeds; cook until seeds start to pop, 2 to 3 minutes. Stir cumin mixture into rice-lentil mixture.
Tear curry leaves roughly and stir into rice-lentil mixture; stir in ginger. Season with salt.
Heat remaining 1 tablespoon ghee in a skillet over medium-high heat; cook and stir cashews until toasted and fragrant, 2 to 4 minutes. Garnish rice-lentil mixture with toasted cashews.