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Combine the soy sauce, wine or sherry, ginger, cornstarch and sugar in a small bowl and whisk until the cornstarch is dissolved. Transfer 2 tablespoons of the sauce to a medium bowl. Place the tempeh in the medium bowl and toss to coat; set aside.
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Cut the white ends off of the scallions; thinly slice the white parts, then cut the green parts into 1-inch pieces. You'll use the white parts and green parts at different times in the recipe, so keep them separate.
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Heat 1 tablespoon of the oil in a large nonstick skillet or wok over medium-high heat until shimmering. Add the white parts of the onion and cook until starting to brown, about 2 minutes. Add the snow peas or snap peas, mushrooms, asparagus, carrot, garlic, and green parts of the onions and stir-fry until crisp tender, about 2 minutes. Transfer to a plate; set aside.
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Heat the remaining 2 tablespoons of oil in the skillet over medium-high heat. Add the tempeh and spread into a single layer. Stir-fry until lightly browned, about 5 minutes.
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Add the noodles and reserved vegetables to the skillet. Cook, tossing with tongs, until heated through, about 2 minutes. Whisk the sauce again to dissolve the cornstarch, then pour it into the pan. Toss until the sauce evenly coats the noodles and vegetables, then remove from heat. Divide into serving bowls and garnish with sesame seeds, if desired.