Add the steak to the bowl of your slow cooker.
In a medium mixing bowl, whisk together the broth, soy sauce, sugar, oil, garlic, & sriracha until evenly combined. Pour over the steak, stirring to combine.
Put the lid on and cook on low for 4 hours.
In a small bowl, stir together 2 tbsp cornstarch and 4 tbsp of the broth from the slow cooker until evenly combined. Pour into the slow cooker, stirring to combine. Cook another 30 minutes to thicken the sauce.
Turn the heat up to high, stir in the broccoli, and cook another 30 minutes.
Serve hot over cooked jasmine, or basmati, white rice.