Wrap tofu in paper towels and press for 30 minutes. Cut into 1-inch cubes and toss with cornstarch, salt, and pepper.
Heat 2 tablespoons of oil in a large skillet over medium-high heat. Add tofu and cook, turning occasionally, until golden brown and crispy. Remove from skillet and set aside.
Add remaining oil to skillet. Add onion and sauté until softened. Stir in curry paste and cook for 1 minute.
Add broccoli, bell pepper, and sweet potato. Sauté until slightly softened.
Pour in coconut milk and vegetable broth. Bring to a simmer, then reduce heat and cook until vegetables are tender.
Stir in crispy tofu, soy sauce, and lime juice. Taste and adjust seasonings.
Serve over rice and garnish with cilantro and sesame seeds.