Whisk together mayonnaise, Sriracha, ketchup, rice vinegar, sugar, garlic powder, and salt for the Yum Yum Sauce in a small bowl until smooth and well combined. Cover and refrigerate until ready to use.
Whisk together soy sauce, brown sugar, sesame oil, water, and garlic in a bowl; set aside.
Bring a large saucepan of water to a boil over medium-high heat. Add yakisoba noodles and cook for 1 minute. Drain and set aside to cool slightly.
Heat oil in a wok or large skillet over medium-high heat. Add broccoli and cook until softened and lightly browned, 3 to 4 minutes. Remove from wok using a slotted spoon and set aside.
Add butter to the wok. When melted, add chicken in a single layer, working in two batches if necessary. Cook until lightly browned on all sides and cooked through (an instant-read thermometer inserted into the thickest part should read at least 165 degrees F (74 degrees C)), about 5 minutes per batch.
Pour in soy sauce mixture. Let mixture come to a simmer, and cook until sauce has slightly thickened, about 5 minutes.
Add broccoli and noodles to the wok. Toss until everything is evenly coated in sauce and heated through.
Garnish with green onions and sesame seeds. Serve with Yum Yum sauce. Recipe developed by Barrett Heald
