In a large skillet or wok, heat 1 tbsp. canola oil over medium-high. Add the tofu in a single layer. Cook, without stirring, until browned on the bottom, about 4 minutes, then cook, stirring gently, until browned on all sides, about 6 minutes more. Transfer to a medium bowl and toss with the hoisin sauce, sugar and sesame oil; season.
In the same skillet, heat the remaining 2 tbsp. canola oil over medium-high. Add the mushrooms, toss to coat and season. Cook, without stirring, until browned, about 2 minutes, then cook, stirring, until any liquid evaporates, about 2 minutes more. Add the leeks and cook, stirring, until crisp-tender, about 2 minutes. Stir in the peas and cook until heated through, about 2 minutes. Gently stir in the tofu; season. Serve with the rice.