Place lemongrass, red chili peppers, ginger, and garlic into blender. Pulse the ingredients into a paste, mix in fish sauce. Pour the marinade over the chicken and let it sit for a few minutes to a couple hours. Grill chicken until it reaches an internal temperature of 150°. Remove from heat, place in foil and wrap tight to keep warm until your ready to serve.
Make the noodles according to a mage directions. Rinse in cold water and set aside.
To make the salad dressing, heat 2 tablespoons of olive oil, in a small saucepan, over medium heat. Sauté minced ginger and garlic until aromatic. Stir in chili sauce followed by peanut butter, maple syrup, soy sauce, coconut milk and lime juice. Bring to a boil. Add salt and pepper, to taste. Remove pan from heat and transfer the peanut dressing into a bowl.
Lightly sauté the mushrooms, transfer to a large mixing bowl. Add in noodles, bean sprouts, carrots and cucumber. Toss to coat ingredients with the peanut dressing.
Place noodle salad on a plate. Cut chicken into 5 strips and arrange them on top of the salad. Before serving, sprinkle with some crushed peanuts, chopped fresh cilantro, and a squeeze of fresh lime juice.