1. Rinse and drain tofu. Cut into 1/2-inch-thick slices and pat dry with paper towels then cut into 1/2-inch cubes.
2. In a 1-cup glass measure, mix broth, vinegar, soy sauce, cornstrach, and chili flakes until smooth.
3. Set a 10- to 12-inch nonstick frying pan over high heat. When hot, add 1 teaspoon oil and the soybeans, stir until beans are hot and their skins are slightly blistered, 2 to 3 minutes. Pour into a bowl.
4. Add remaining 2 teaspoons oil, the ginger, and garlic to pan; stir just until garlic begins to brown about 15 seconds. Add tofu to pan and stir occasionally until tofu is hot and lightly browned, 2 to 3 minutes. Return beans to pan. Stir broth mixture and add to pan; stir until sauce boils and thickens. Add salt to taste. Pour into a serving dish.