Combine soy sauce, vinegar, and red pepper flakes into a bowl. Add beef and mix well. Marinate in the refrigerator for 15-30 minutes.
Break up ramen noodles into a microwave safe bowl. Pour enough water in the bowl to cover the noodles, about 2-3 cups, and microwave on HIGH for 3 minutes. Set aside and wait to drain the water until later in the recipe. Discard the seasoning packet.
Meanwhile, cut broccoli into small florets, leaving out the stems. Steam broccoli in a steamer, or cook the broccoli in boiling water until tender, about 6-8 minutes. Set aside.
Mix the broth and cornstarch in a cup and set aside.
In a large stir-fry pan, cook garlic and ginger in oil for 30 seconds.
Add beef and cook 2 minutes.
Add bell peppers and cook an additional 2 minutes.
Toss in broccoli and green onion. Stir-fry until heated through, about 2 minutes. Add cornstarch mixture. Bring to a boil and allow to cook until the liquid thickens, about 3-5 minutes.
Drain Ramen noodles.
Serve 3/4 cup beef/broccoli mixture over 1/4 cup cooked Ramen noodles and top with 1 teaspoon cashews (about 3-5 cashews).