Cut the tofu into triangles. Do this by cutting the block in half, lengthwise, then cut each half into into quarter to half inch slices. Cut the slices in half on a diagonal to create triangles (Note 1).
To make the sauce, first stir the cold water and cornstarch together in a small bowl or container. Keep stirring until the cornstarch is completely dissolved, then stir in the remaining ingredients.
Coat the bottom of a large wok with 1 tablespoon of the oil and place it over medium heat. Give the oil a minute to heat up, then add the tofu triangles in a single layer (Note 2). Cook the tofu for about five minutes on each side, until golden brown and crispy. Transfer the pieces to a plate when they're done.
Add the remaining tablespoon of oil to the wok and turn the heat up to medium-high. Add the sugar snap peas and carrots. Stir-fry the vegetables for 2 to 3 minutes, until they brighten in color a bit and become tender-crisp.
Push the vegetables to the side to create a space in the middle of the wok, then add your garlic and ginger. Sauté the aromatics for about 30 seconds, until they become very fragrant, stirring constantly to prevent burning.
Stir the garlic and ginger in with the vegetables. Return the tofu to the wok. Give the sauce a quick stir to redistribute any cornstarch that has settled to the bottom, then carefully pour the sauce over the tofu. Stir everything up and continue to stir-fry the mixture for 1 to 2 minutes, until the sauce thickens and coats the tofu and veggies.
Remove the wok from heat. Stir in the scallions.
Serve immediately over rice.