Combine 1/2 cup soy sauce, honey, balsamic vinegar, rice vinegar, peanut butter, molasses (if using), 1 tablespoon ginger, 1 clove garlic, and 1/3 cup water in a bowl. Whisk until smooth.

Cook noodles according to package directions. Drain. Meanwhile, in the pot used to cook noodles, combine broth and 1/2 of the soy sauce mixture. Bring to a simmer over medium heat, stir in spinach (if using). Keep warm.

Heat 1 tablespoon sesame oil in a large skillet over medium-high heat. When the oil shimmers, add mushrooms. Cook undisturbed for 5 minutes or until golden. Add 1 sliced shallot, 1 tablespoon ginger, and 2 cloves garlic. Cook 4-5 minutes, until fragrant. Add 2 tablespoons soy sauce and a pinch of black pepper. Cook another 2-3 minutes, until mushrooms are caramelized. Add 1/4 cup toasted sesame seeds, cook 2 minutes. Spoon mushrooms out onto a plate.

To the skillet, add the remaining soy sauce mixture and bring to a simmer over medium heat. Add the cooked noodles, toss to combine, and cook until the sauce just coats the noodles, 2-3 minutes. Remove from heat.

Ladle the warm broth into bowls. Add the saucy noodles and toss to combine. Spoon the caramelized mushrooms over the noodles. Top with 2 sliced green onions and chili oil to taste. Enjoy!