In a shallow bowl, combine the all-purpose flour, garlic powder, onion powder, salt, and pepper. Mix well.: You will notice the dry mixture becomes aromatic as the garlic powder and onion powder bloom in the flour, offering a warm, toasty scent that promises depth. Use a shallow bowl so you can coat the steaks evenly. Stir thoroughly until the seasonings are uniformly distributed, which prevents salty pockets. A common mistake is failing to mix well, which leads to uneven seasoning and clumps that stick to the meat. The texture should be light and powdery with no lumps, and the aroma should be balanced between savory and faintly sweet from the onion powder.
Season both sides of the cube steaks with salt and pepper. Dredge each cube steak in the seasoned flour mixture, shaking off any excess.: As you press the cube steak into the flour, you should feel a dry, powdery coating adhere to the meat. The light coating helps form a crisp exterior when it hits the hot oil, and shaking off excess prevents a gummy crust. The flour should cling in a thin, even layer, not a paste. Avoid overcoating which causes thick, undercooked pockets of flour inside the crust. The goal is a delicate, even dusting so the steak develops a golden brown crust and the sauce thickens naturally from the leftover seasoned flour in the pan.
In a large skillet, heat the olive oil over medium-high heat. Add the cube steaks to the skillet and cook for 3-4 minutes on each side, or until they are browned and cooked to your desired level of doneness. Remove the steaks from the skillet and set them aside.: When the olive oil shimmers and you hear a clear sizzle, slide the steaks in and resist moving them too soon. You want that audible sear and a deep, nutty aroma as proteins brown. Visual cues include a golden to deep brown crust and edges pulling slightly away from the pan. If the pan is overcrowded, the steaks will steam and not brown, so cook in batches if needed. After searing, the steaks will continue to finish in the sauce so you can err slightly under done here, especially since they will simmer later and absorb flavors.
In the same skillet, add the sliced onions and cook until they are softened and translucent. Add the butter and let it melt with the onions. Sprinkle the onion soup mix over the onions and butter, stirring to combine. Pour in the beef broth, stirring continuously to avoid lumps. Bring the mixture to a simmer and add the sliced mushrooms.: The residual fond in the pan holds intense flavor, and scraping it up with the onion as it softens releases that depth into the base. As the butter melts, it carries the sweetness of the onions, and the onion soup mix dissolves into a fragrant seasoning that smells savory and rich. When you pour the beef broth in, stir so any leftover flour blends smoothly, preventing graininess. The sauce should move from watery to slightly glossy as it comes to a gentle simmer, and the mushrooms will start to exhale an earthy perfume. A common misstep is boiling vigorously which can over reduce the liquid and concentrate saltiness, so aim for a steady simmer.
Place the cooked steaks back into the skillet, ensuring they are nestled in the onion and mushroom mixture, cover, and simmer for another 10 minutes.: As the steaks rest in the simmering gravy, you will see the sauce thicken and cling to the meat, and the aromas will deepen into a comforting, savory bouquet. The covered pan traps steam which helps the cube steak finish tenderly while it soaks up the sauce. Use this time to watch for gentle bubbling and a glossy sheen on the gravy, that signals the starches from the flour have integrated. Avoid leaving the heat too high, which can over reduce the sauce and toughen the meat. When ready, the steaks should feel tender to the fork and the sauce should coat a spoon with a smooth, velvety finish.