Heat oil in a large saucepan over medium heat and cook onion, garlic, and ginger, stirring often, until soft and translucent, about 3 minutes. Add sweet potatoes and cook for an additional 2 minutes. Dust with curry powder and cook for 30 seconds.
Stir tomatoes and their juices into the pot. Add vegetable stock and bring to a boil. Reduce heat to medium-low, cover, and cook until sweet potatoes are soft, 12 to 15 minutes. Add peas and simmer for another 5 minutes. Season with salt and pepper. Stir in tofu and carefully mix together. Heat for 3 minutes. Garnish with fresh mint leaves.