Pat the round steak dry with a paper towel. Tenderize the beef by pounding with a tenderizer.
Cut into approximate ¼ pound pieces about 4 inches square. This does not need to be exact.
Sprinkle both sides of beef with kosher salt and Creole seasoning. Set aside.
Slice yellow onions in half crossways, then slice each half into half-rings. Slice bell pepper in half, crossways, then into half-rings. Roughly chop garlic. Slice or quarter the mushrooms, if using.
Mix the Herb and Spice Blend in a small prep bowl and set aside. Measure all the remaining ingredients and set them aside.
In a cast-iron Dutch oven, heat the vegetable oil over medium-high heat until it shimmers.
Season about 1 cup of AP Flour with kosher salt and ground pepper, then dredge the beef in it. Shake off the excess flour and carefully add it to the hot oil a piece at a time. Make sure not to overcrowd the Dutch oven, so do this in batches.
Brown the floured beef for about 1 minute on each side. Remove the beef and set it aside.
Once all the beef has been browned, lower the heat to medium and add the butter. When the butter is bubbly, add the mushrooms (if using) and saute another 5 minutes.
Next add the yellow onions and bell peppers. Saute, stirring often for about 15 minutes until the onions are starting to caramelize.
Add the garlic and about ½ of the Herb and Spice Blend without the bay leaves. Saute until aromatic, about 2 minutes.
Add the 2 tablespoons of AP flour and mix well into the vegetables. Saute for about 5 minutes until the flour taste has cooked off.
Add the remaining Herb and Spice Blend, the bay leaves and Worcestershire sauce. Stir to thoroughly combine and saute for about 2 to 3 minutes.
Increase the heat to high, add the stock and bring to a low boil. Lower the heat to maintain a heavy simmer for about 5 minutes.
Add the browned beef back to the gravy and stir so that all the beef is coated with gravy.
Lower the heat. Cover the Dutch oven and simmer for about 2 ½ to 3 hours, until the beef is very tender and pulling apart. Stir occasionally so that it does not stick to the bottom.
Taste for seasoning and add more salt, pepper, or creole seasoning if needed. Add more stock if the gravy gets too thick.
When the beef is very tender, remove the Dutch oven from the heat and let it sit for about 10 minutes, covered. Remove the bay leaves and serve.
Notes
Leftovers can be stored in the refrigerator for 3 to 4 days and in the freezer for up to 3 months. Leftovers should be stored in an airtight container. Defrost frozen leftovers in the fridge overnight. Reheat on the stove, very low simmer until warmed through, about 15 to 20 minutes.Top Round (bone-in or boneless) is recommended although Bottom Round will work.