In a large skillet, brown the ground beef and onion until beef is fully cooked.

In a bowl, combine the ketchup, mustard, soy sauce, brown sugar, Sriracha sauce, and water for the sauce. Add 4 Tbsp of the sauce mixture to the beef and cook for 1 minute.

Make a well in the middle of the skillet and add the broccoli florets to the well. Drizzle on the remaining sauce over the broccoli and then stir to combine. Cook everything together until the broccoli is vibrant green and ender. Taste and adjust with salt and pepper if needed. Serve over a bowl of hot rice. Serves 4-5.