Preheat oven to 375°. In a large microwave-safe bowl, combine frozen mixed vegetables, potato, cauliflower and water. Cover and microwave on high for 8-10 minutes or until potato is almost tender; drain. Cut tofu into 1/2-in. cubes; pat dry with paper towels. In a large bowl, combine cornstarch and onion salt. Add tofu and toss to coat. In a large skillet, heat oil over medium-high heat. Add tofu; cook until crisp and golden brown, 5-7 minutes, stirring occasionally. Remove from pan; drain on paper towels. In a large bowl, whisk eggs, soup, milk, thyme, pepper and salt until combined. Stir in vegetable mixture and tofu. On a lightly floured surface, roll one half of dough to a 1/8-in.-thick circle; transfer to a 9-in. pie plate. Trim even with rim. Add filling. Roll remaining dough to a 1/8-in.-thick circle. Place over filling. Trim, seal and flute edge. Cut slits in top. Bake on a lower oven rack until crust is golden brown and filling is bubbly, 45-50 minutes. Let stand for 15 minutes before cutting.