Step 1: In a shallow bowl, combine the all-purpose flour, salt, and black pepper. Whisk them together until well mixed.
Step 2: Dredge each cube steak thoroughly in the flour mixture, ensuring both sides are well coated. Gently shake off any excess flour.
Step 3: Heat the vegetable oil in a large skillet over medium-high heat. Once hot, carefully add the dredged steaks to the skillet.
Step 4: Cook the steaks for 3-4 minutes per side, or until they are nicely browned. Remove the browned steaks from the skillet and set them aside on a plate.
Step 5: In the same skillet, add the sliced onion. Cook over medium heat, stirring occasionally, until the onion softens and becomes translucent, about 5-7 minutes.
Step 6: Stir in the can of cream of mushroom soup and the milk. Mix well, scraping up any browned bits from the bottom of the skillet. Bring the sauce to a gentle simmer.
Step 7: Return the browned steaks to the skillet, nestling them into the simmering sauce. Make sure each steak is coated with the gravy.
Step 8: Reduce the heat to low, cover the skillet, and let the steaks simmer for an additional 15-20 minutes, or until the steaks are very tender. The simmering time allows the flavors to meld beautifully and tenderizes the meat.
Step 9: Before serving, garnish the steaks with freshly chopped parsley and a sprinkle of grated Parmesan cheese, if desired. A pinch of red pepper flakes can add a nice subtle kick.
Step 10: Serve immediately with your favorite sides.