Make sure you have cooked your spaghetti squash ahead of time, either by cooking it in the Instant Pot or in the oven. You can use cold or hot noodles for this recipe, so feel free to cook it ahead of time and store it in your fridge for up to 5 days in advance. If you're cooking the squash right away, chop the other vegetables as it cooks to be efficient with your time. Use a fork to shred the flesh of the cooked spaghetti squash into "noodles" and set aside.: The bowl of the recipe will smell subtly sweet and toasty when the squash is cooked correctly, with tender flesh that pulls into strands when scraped. When you shred the flesh with a fork you should hear a faint tearing sound and see long noodle like strands that are moist but not watery. This matters because undercooked squash will be firm and underwhelming, while overcooked squash becomes mushy and limp, losing the noodle effect. If your squash seems watery, drain it briefly in a colander and blot with paper towels. A common mistake is shredding while the squash is too hot which can release excess steam and water, so let it cool slightly if you plan to store it for later use.
Heat the oil in a large skillet, and sauté the onion, celery, and carrots until they are crisp-tender, about 8 minutes. Use a splash of water, if needed, to prevent sticking. Add in the garlic and ginger and stir for one more minute, just until fragrant.: Chilled squash has a firmer texture and a slightly different mouthfeel, which can be pleasing when you want a quicker reheat, while warm strands will meld into the sauce more readily and taste freshly made. Store in an airtight container to preserve texture and prevent drying, and when reheating add a small splash of water or oil to revive the strands and prevent sticking. The key reason to prep in advance is time savings on busy nights, however avoid storing it beyond the suggested window as the texture will degrade and the squash may become watery.
Once the veggies are cooked to your liking, add in the tamari to taste, starting with just 3 tablespoons, maple syrup, and the spaghetti squash "noodles.": While the squash softens, the kitchen fills with a light roasted aroma, a good cue to begin prepping the aromatics. Chop the onion , celery , and carrots to similar sizes so they cook evenly and produce a pleasing mix of tender and crisp bites. Efficiency here saves you from overcooking components, and having mise en place reduces stress once you start the skillet. One trap is rushing the chop and ending up with mismatched pieces that cook unevenly, so take a few extra minutes to keep sizes consistent.
Toss well to heat everything thoroughly and adjust the seasoning, adding sea salt and more tamari if desired. (You may also need another splash of water at this point to prevent sticking.): When you fork the squash you will notice the strands separate cleanly, and they should look glossy, not dull, indicating they retained moisture without being soggy. Shredding releases a subtle sweet scent that pairs well with the sauté aromas to come. Set the strands aside in a bowl to keep them warm or chilled based on your plan, and avoid overmixing which can break the delicate strands into shorter pieces. A common issue is using too much force which can mash the squash, so gently coax the flesh into strands instead of aggressive scraping.
Add the fresh spinach at the very end, as it will wilt quickly from the heat, then serve warm with a garnish of chopped green onions on top. Leftovers can be stored in the fridge for up to 3 days in an airtight container.: As the vegetables hit the hot pan you will hear a gentle sizzle and soon smell the onion sweetening and the carrots softening, creating a layered savory aroma. Keep the heat moderate so the vegetables cook through without burning, stirring occasionally to encourage even browning. If the pan seems too dry, add a splash of water to deglaze and prevent sticking while preserving moisture. Avoid cranking the heat which can char the exterior before the interior softens, leading to uneven texture.
Use a splash of water, if needed, to prevent sticking: The small hiss of water hitting the skillet helps lift flavorful browned bits without adding oil, and it keeps the vegetables moving so they cook evenly while maintaining moisture. This technique preserves color and prevents scorching when the pan becomes dry, especially important if you are using a stainless steel skillet. Be cautious not to add too much liquid which can steam the vegetables and strip away desirable caramelization, resulting in bland texture.
Add in the garlic and ginger and stir for one more minute, just until fragrant: The moment you add minced garlic and ginger you will notice the aroma sharpen and brighten, signaling that the base is ready to receive sauce. Move quickly so these aromatics release their oils but do not brown, which would impart bitterness. Stir gently and pay attention to the minute when their fragrance blooms; if you smell any burnt notes, reduce heat immediately. Overcooking these fine aromatics is a frequent misstep, so keep them moving in the pan.
Once the veggies are cooked to your liking, add in the tamari to taste, starting with just 3 tablespoons, maple syrup, and the spaghetti squash "noodles": When the sauce hits the pan you will see a sheen form on the vegetables as the Tamari glazes them, and the maple syrup, if used, will add a subtle gloss and rounded sweetness. Toss so the strands of spaghetti squash are coated and warmed through, absorbing the savory sauce. This step matters because it allows flavors to marry and for the squash to carry the seasoning; a common error is adding too much sauce at once which can oversalt the dish, so add gradually and taste.
Toss well to heat everything thoroughly and adjust the seasoning, adding sea salt and more tamari if desired: As you toss, listen for a gentle sizzle and watch for steam to rise, which indicates the components are coming together. Taste frequently and adjust with small additions of sea salt or more Tamari to reach balance, remembering that Tamari contributes most of the salt. If the pan seems sticky, a splash of water helps loosen the mixture without diluting flavor. Avoid assuming the first bite reflects the final balance; flavors often deepen as the dish rests briefly off the heat.
Add the fresh spinach at the very end, as it will wilt quickly from the heat, then serve warm with a garnish of chopped green onions on top: When you add the fresh baby spinach you will see it collapse in seconds, turning glossy and bright green, which signals it is ready. Finish with the chopped green onions to add a crisp, fresh counterpoint and release a sharp, grassy scent. Serve right away so textures remain distinct, as leaving it too long will let the spinach and squash soften further and lose their contrast. A typical slip is overcooking the spinach, so add it literally at the last moment.
Leftovers can be stored in the fridge for up to 3 days in an airtight container: Properly cooled and sealed, the flavors will meld and the dish will keep well for several days, making it an excellent leftover meal. Reheat gently in a skillet with a splash of water or oil to revive the texture and prevent drying out, and taste before serving to adjust seasoning. Beware of reheating too aggressively in the microwave which can make the squash watery and the vegetables limp, detracting from the original textural interplay.