Cut the Skirt Steak (1 pound) into half and trim the fat by gliding the knife underneath the fat.
Add Chicken Stock (4 cup), skirt steak, Onion (3), Bell Pepper (2), Bay Leaf (2), and Dried Oregano (2 tablespoon) to the pressure cooker. Put the lid on and cook on high pressure for 1 hour 15 minutes.
After 1 hour 15 minutes, remove skirt steak from the broth and shred the skirt steak using two forks. Drain 1 cup of broth and set aside.
Preheat the oven to 400 degrees F (200 degrees C).
To prepare the gravy, Melt Butter (4 tablespoon) in a pan and add Olive Oil (2 tablespoon).
Add Baby Bella Mushroom (1/2 cup) into the pan and cook for a minute before adding in Onion (1). Cook for another minute.
Add All-Purpose Flour (3 tablespoon), 1 cup of reserved broth and mix everything together. As the broth starts to thicken, add in Red Chili Pepper (to taste), Kosher Salt and Freshly Ground Black Pepper (to taste).
Add the shredded beef into the pan and stir to give it a nice coating.
Split Buns (12) into half and place half a slice of Provolone Cheese (6 slice) on one side of each bun. Lay the pulled beef on top of the cheese along with some onions and bell peppers. Add another layer of cheese.
Mix Butter (4 tablespoon) and Garlic Powder (2 teaspoon).
Place the other half of the bun on top of the cheese. Brush the top of the buns with the melted butter and garlic powder.
Put the buns into the oven and bake for about 15 mins. After 15 mins, take it out of the oven and serve!