Lay the sirloin steak strips into the bottom of the slow cooker insert and sprinkle with salt and pepper.
In a medium bowl, whisk together 1 cup beef broth, soy sauce, coconut sugar, sesame oil, garlic, ginger, rice vinegar, scallions, and red pepper flakes.
Pour the sauce over the sirloin strips and cover and cook on low for 5 hours or high for 2-3 hours.
In a small bowl, add the last ½ cup of beef broth and whisk in the cornstarch until it's dissolved - this is your slurry.
Stir the cornstarch slurry into the slow cooker with sauce and beef.
Place the lid back on and cook for another 20-30 minutes or until the sauce thickens.
Cook the frozen broccoli in the microwave according to the package instructions.
Add the broccoli with the rest of the ingredients and stir to combine.
Serve this healthy beef and broccoli over cooked brown rice and garnish with sesame seeds.