Slice skirt steak in half lengthwise so it fits in a single layer inside slow cooker.
Sprinkle top with dry onion soup mix, pouring beef broth over the top.
Cover and cook on low for 6-8 hours ideally, or on high for 3-4 hours or until very tender and easy to slice.
To make the gravy put ingredients for gravy in a saucepan (keeping cornstarch aside to whisk together with cool water) over medium high heat. Stir. When bubbling pour in cornstarch & water slurry and stir so it can thicken. Serve on top of sliced skirt steak.