Heat a Dutch oven over medium heat. Add curry powder, garam masala and mustard seeds and toast, stirring, until spices begin to darken, about 1 minute. Transfer to a small bowl.
Add oil, onion, garlic, ginger and salt to pot and cook, stirring, until softened, 3-4 minutes
Stir in eggplant, cauliflower, tomatoes, chickpeas, water and the reserved spices. Bring to a simmer. Cover, reduce heat and cook, stirring occasionally, until vegetables are tender, 15-20 mins.
top each serving with a dollop of yogurt if desired.