1. In a 10-inch skillet, warm 1 tablespoon of the sesame oil over medium-high heat until simmering.
2. Add the tempeh and cook until browned, about 2 minutes, then flip and cook for an additional 1 to 2 minutes. Transfer to a plate.
3. Add the remaining 2 tablespoons sesame oil to the skillet and heat until simmering. Add the onion, carrot, broccoli, and cabbage and cook, stirring occasionally, until the vegetables are slightly softened, 3 to 4 minutes. Stir in the ginger, stock, tamari, and tempeh, then remove pan from the heat
4. While the tempeh and vegetables cook, in a medium saucepan, bring 4 cups filtered water to a simmer over medium-high heat. Add the kelp noodles and cook just until heated through, about 3 minutes. Drain noodles in a colander.
5. Add the noodles to the skillet, return the skillet to medium-high heat, and toss until the noodles are well combined with the tempeh and vegetables.
6. Toss in the scallion greens and serve.