Ingredients
1/2 medium white onion, sliced thinly
2 tsp. light brown sugar
1 tbsp. Worcestershire sauce
2 tbsp. salted butter
2 lbs. skirt steak or sirloin steak
1 tsp. garlic powder
salt and pepper, to taste
1/2 cup mushrooms, sliced
2 medium green bell peppers, sliced thinly
1 tbsp. soy sauce
3 cups beef stock/broth
1/4 cup chopped fresh parsley

Instructions
Combine onions, brown sugar, and Worcestershire sauce in a slow cooker.
Stir around and add in butter and steak. Season meat with garlic powder, salt, and pepper.
Add sliced mushrooms and green bell peppers to the slow cooker. Pour beef broth and soy sauce over everything, reserving 1/2 cup of the beef broth for later.
Cover the slow cooker and cook on LOW for 6-8 hours (alternately, you can cook on HIGH for 5-6 hours), being sure to toss and add the other 1/2 cup beef broth about halfway through the cook time.
Turn off heat or set to warm and stir in chopped parsley.
To serve, spread mayonnaise on each hoagie roll and load it up with the steak mixture.
Top with cheese, wrap in foil, and bake at 400 for about 5-10 minutes to allow the cheese to melt.

Credit: Susan Recipe