In a bowl, whisk together egg whites, remaining 3 tablespoons cornstarch, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Add tofu, and toss to coat.
3. In a large nonstick skillet, heat 1 tablespoon oil over medium-high. Lift half the chicken from egg-white mixture (shaking off excess), and add to skillet. Cook, turning occasionally, until golden, 6 to 8 minutes. Transfer to a plate; repeat with remaining oil and tofu, and set aside (reserve skillet).
4. Add snow-pea mixture to skillet. Cover; cook until snow peas are tender and sauce has thickened, 3 to 5 minutes. Return chicken to skillet (with any juices); toss to coat. Serve with rice.