Preheat the oven to 400°F.
Pat the steak pieces completely dry. Season with salt, pepper, CTH, garlic powder, and onion powder. Heat the olive oil in a 12-inch cast iron skillet over medium-high heat. Sear the steak for 2 to 3 minutes until browned — it doesn't need to cook through at this stage. Remove to a plate.
Reduce the heat to medium. Add the butter and sliced onion to the same skillet. Cook for 6 to 8 minutes, stirring occasionally, until the onions are soft and golden. Add the garlic and cook for 30 seconds.
Stir in the Worcestershire sauce and flour and cook for 1 minute. Slowly pour in the beef broth while stirring and scrape up every browned bit from the bottom of the skillet.
Stir in the heavy cream, Dijon, and thyme. Simmer for 2 to 3 minutes until the gravy begins to thicken. Taste and adjust salt and pepper. Stir in the drained peas.
Return the steak and any accumulated juices to the skillet. Stir to combine. The gravy should be a little looser than you'd normally want — it'll thicken in the oven. Remove from heat.
In a bowl, stir together the Jiffy mix, egg, milk, and melted butter just until combined. Don't overmix.
Dollop the cornbread batter over the steak mixture. Leave some gaps — the gravy bubbling up through those spaces while it bakes is half the appeal.
Bake uncovered for 18 to 22 minutes until the cornbread is golden brown and cooked through.
Brush the hot cornbread immediately with melted butter. Let the skillet rest for 5 minutes before scooping and serving.