Slice the onion, mince the garlic and grate or mince the ginger. In a small bowl, mix the soy sauce, rice vinegar, sesame oil and optional maple syrup. Preparing the sauce before cooking makes the stir-fry easier to assemble because everything comes together quickly once the pan is hot.

Bring a pot of water to a boil and cook the soba noodles according to the package directions. Drain and rinse briefly under cool water to remove excess surface starch and help prevent sticking. Drain thoroughly. If you're not adding them to the pan immediately, toss them with a small amount of neutral oil.

Heat the neutral oil in a large skillet or wok over medium-high heat. Add the onion and cook until softened and beginning to brown. Stir in the garlic and ginger and cook briefly until fragrant, taking care not to burn the garlic. These aromatics create the flavor base for the noodles.

Add the Beyond Steak and cook according to its package directions, allowing the pieces to brown where possible. Stir in the peas and cook until heated through. Add the spinach and toss until just wilted. If the pan seems dry, add a small splash of water to help the vegetables cook without scorching.

Add the cooked soba noodles to the skillet, pour in the soy-vinegar mixture and toss everything together until the noodles are coated. Add a splash of water if needed to loosen the sauce. Taste and adjust with more soy sauce for saltiness, vinegar for tang or sesame oil for nuttiness.

Remove the pan from the heat and divide the noodles among bowls. Finish with sliced scallions and sesame seeds. Add chili flakes or chili crisp if you want some heat, or serve with lime wedges for extra brightness. Enjoy immediately while the noodles are warm and glossy.