Peel and discard the outer leaves of the lemongrass. With a sharp knife, cut off and discard the upper half of the stalks at the point where the leaves branch out. Thinly slice the remaining stalks.
Process the lemongrass, chile peppers, and garlic in a food processor until finely ground. Transfer the mixture to a mixing bowl. Add the chicken and the remaining marinade ingredients, mixing together until throughly blended. Cover and refrigerate for 30 minutes.
When ready to stir-fry, heat a wok or large skillet over high heat. Add the 1 tablespoon of peanut oil and heat until smoking-hot. Add onions and stir-fry until golden brown, about 2 minutes.
Add the marinated chicken and stir-fry until the chicken is golden on the outside and just cooked through on the inside, about 5 minutes. Add the broth, coconut milk, fish sauce and sugar and bring to a boil. Stir in the cellophane noodles and mushrooms. Continue to cook for a minute longer, then remove from the heat and stir in the scallions. Transfer the stir-fry to a warm platter and serve immediately.
From The Best of Nicole Routhier, published by Stewart, Tabori & Chang Marinade and Chicken