Step 1: In a medium bowl, whisk together the cream of mushroom soup, cream of chicken soup, onion soup mix, garlic powder, black pepper, and water or beef broth until well combined.
Step 2: Lightly spray the inside of your crockpot with nonstick cooking spray. Place the cube steaks in a single layer at the bottom. If necessary, you can stack them with a little sauce in between layers to prevent sticking.
Step 3: Pour the prepared sauce mixture evenly over the cube steaks, ensuring all the meat is fully covered to promote even cooking and maximum tenderness.
Step 4: Cover the crockpot with its lid. Cook on LOW for 6-8 hours or on HIGH for 4-5 hours. Avoid lifting the lid during cooking to prevent heat loss and ensure efficient cooking.
Step 5: If a thicker gravy is desired, prepare a cornstarch slurry by mixing 1 tablespoon of cornstarch with 1 tablespoon of cold water. Stir this slurry into the crockpot about 30 minutes before the end of the cooking time. Stir gently and allow the gravy to thicken with the lid slightly ajar.
Step 6: Once the steaks are fork-tender and the gravy has reached your desired consistency, turn off the slow cooker. Garnish with fresh chopped parsley or a sprinkle of black pepper before serving. Serve hot over mashed potatoes, rice, or egg noodles.