Bring a large pot of water to a boil and cook the noodles according to the package instructions. Just before draining, carefully reserve 120 ml (120 ml) of the starchy noodle cooking water.

While the noodles cook, prepare the sauce base in a large mixing bowl. Whisk together the tahini, white miso paste, soy sauce, toasted sesame oil, maple syrup, grated garlic, and grated ginger until a thick, uniform paste forms.

Gradually pour half of the hot noodle water into the bowl with the paste, whisking continuously until the mixture transforms into a smooth, creamy sauce.

Add the hot, drained noodles and the fresh baby spinach directly into the bowl with the sauce. Toss everything vigorously together. The residual heat from the noodles will wilt the spinach perfectly within seconds. Add more reserved water if you prefer a looser consistency.

Divide the coated noodles into bowls. Garnish with the sliced green onions, toasted sesame seeds, and a drizzle of chili oil if desired. Serve immediately.