In a medium bowl, whisk together peanut butter, soy sauce, rice vinegar, brown sugar, grated ginger, and sriracha. Mix until smooth and creamy. Set the sauce aside while you prepare the remaining ingredients.
Bring a large pot of salted water to a boil and cook the noodles according to the package instructions. Before draining, reserve about half a cup of pasta water. Drain the noodles and set them aside.
Heat one tablespoon of avocado oil in a large skillet over medium-high heat. Add the ground chicken and cook until browned and fully cooked through. Season lightly with salt and pepper while cooking.
Add the remaining oil to the skillet along with the white parts of the scallions and sliced bell pepper. Cook for several minutes until the vegetables become tender-crisp. Stir in the minced garlic and cook until fragrant.
Mix the baby spinach into the skillet and allow it to wilt. Stir continuously so the spinach cooks evenly. This step adds color, texture, and nutrients to the dish.
Add the cooked noodles and prepared peanut sauce to the skillet. Toss everything together until the noodles are evenly coated. Add reserved pasta water gradually until the sauce reaches your desired consistency.
Remove the skillet from the heat and transfer the noodles to serving bowls. Sprinkle with chopped roasted peanuts and the green scallion tops. Serve immediately while warm and creamy.