Quick Veggie Pad Thai

Name: Quick Veggie Pad Thai
Ingredients: 12 ounces pad thai noodles (thin rice noodles); 1/2 cup low-sodium soy sauce; 1/2 cup brown sugar; 1/4 cup smooth peanut butter; 2 tablespoons fish sauce; 2 tablespoons chile garlic sauce; 3 limes, zested and juiced; 4 scallions, sliced thin, whites and greens separated; 4 cloves garlic; 3 tablespoons minced fresh ginger; 1/4 cup peanut oil; 1 cup sliced cremini mushrooms; 1 cup sliced shiitake mushrooms; 1 small bunch asparagus, cut into 1-inch segments; 1 large red bell pepper, sliced thin; 1 large egg, beaten; 1 cup bean sprouts, rinsed; 1/2 cup chopped unsalted peanuts; 1/4 cup fresh cilantro; Sriracha for serving, optional