Place the chickpeas into a large container and cover with several cm of cool water; allow to soak for 8 hours or overnight. Drain.
Combine the chickpeas and 3 cups (750ml) water in a large pot over medium heat; cook until the chickpeas are tender but not yet mushy, 30 to 45 minutes. Drain.
Heat the oil in a frypan over medium heat. Fry the brown lentils, mustard seeds and chilli flakes in the hot oil. When the seeds begin to splutter, add the chickpeas, chillis, mango, coconut, curry leaves and asafoetida powder; season with salt. Mix well and cook until completely heated, 2 to 3 minutes. Remove from heat and add the lemon juice. Serve warm or at room temperature.