Set a wire rack on a sheet pan. Warm oven to 200°F to keep steaks crisp.
Stir flour, salt, pepper, paprika, garlic powder, onion powder, and baking powder in a shallow dish.
Whisk buttermilk, eggs, and hot sauce in another bowl until smooth.
Pat cube steaks dry. Lightly season both sides with a pinch of salt and pepper.
Dredge steaks in seasoned flour, dip in buttermilk mixture, then coat again in flour. Press to adhere.
Rest coated steaks on the rack for 10 minutes so the crust sets.
Heat about 1/2 inch vegetable oil in a large skillet to 350°F over medium-high heat.
Fry steaks in batches 3–4 minutes per side until deeply golden. Transfer to rack; keep warm in the oven.
Pour off all but 2 tablespoons fat. Add butter. Sauté mushrooms and onion until browned, 6–8 minutes.
Stir in garlic and thyme for 30 seconds. Sprinkle flour over vegetables and cook 1 minute, stirring.
Whisk in beef broth and milk gradually. Simmer, stirring, until thick and silky, 4–6 minutes.
Stir in Worcestershire. Season gravy with salt and pepper to taste.
Serve steaks smothered with mushroom gravy. Garnish with parsley and enjoy hot.