Place carrots in medium saucepan, add cold water to cover, and heat to boiling. Boil uncovered until tender, about 5 minutes. Drain and cool under cold running water. Blanch corn in medium saucepan of boiling water 30 seconds. Drain and cool under running water. Trim and halve mushrooms. Cut bell peppers lengthwise into thin strips, then cut strips crosswise in half.
Combine scallions, ginger, garlic, and pepper flakes.
Place remaining ingredients except safflower oil in mixing bowl and stir until completely blender. Set sauce aside.
Heat safflower oil in wok or large skillet over medium-high heat until very hot. Add garlic mixture and stir-fry 10 seconds. Add bell peppers and mushrooms; stir-fry until edges of peppers are tender, about 2 minutes. Add sauce and heat to boiling, stirring constantly. Add carrots and corn; toss to coat and heat through. Serve hot.