Step 1: Cook the Noodles. Bring a large pot of water to a boil. Add the noodles and cook according to package directions until al dente. Drain well and set aside.
Step 2: Brown the Beef. Heat vegetable oil in a large skillet or wok over medium-high heat. Add the ground beef and break it apart with a spoon. Cook until browned and crumbled. Drain any excess fat.
Step 3: Add Aromatics. Add the minced garlic and grated ginger to the skillet with the beef. Cook for 1-2 minutes until fragrant, stirring constantly.
Step 4: Prepare the Sauce. In a small bowl, whisk together the soy sauce, brown sugar, water or broth, rice vinegar, cornstarch, and red pepper flakes (if using) until the cornstarch is fully dissolved and the sauce is smooth.
Step 5: Combine Beef and Sauce. Pour the sauce mixture into the skillet with the beef and aromatics. Bring to a gentle simmer, stirring constantly, until the sauce thickens and becomes glossy, about 2-3 minutes.
Step 6: Combine with Noodles. Add the cooked and drained noodles to the skillet with the beef and sauce. Toss gently to coat all the noodles evenly.
Step 7: Garnish and Serve. Remove from heat. Serve immediately, garnished with sliced green onions and sesame seeds. Enjoy!