Dice the yellow onion into 1/4-inch pieces and set aside. In a small bowl, combine the onion powder, garlic powder, dried oregano, paprika, salt, pepper, and dijon mustard—this ensures the spices distribute evenly throughout the dish rather than settling in clumps. Slice the kielbasa into 1/2-inch rounds and shred the cheddar cheese directly from the block (it melts much more smoothly than pre-shredded). Having everything prepped and measured before you start cooking makes the next steps quick and efficient.

In a medium bowl, whisk together the cream of chicken soup, milk, and sour cream until smooth and well combined. This creates your sauce foundation and ensures there are no lumps before it hits the crockpot. Add the spice mixture from Step 1 to this sauce and stir well to incorporate all the seasonings evenly.

Spray the inside of your crockpot with nonstick cooking spray. Add the frozen diced potatoes, sliced kielbasa from Step 1, shredded cheese from Step 1, and diced onion from Step 1. Pour the creamy sauce mixture from Step 2 over everything and stir gently but thoroughly to combine all ingredients and ensure the potatoes are submerged. I like to stir the mixture well at this point so every potato gets coated with the sauce—it helps them cook evenly. Cover and cook on low for 5–6 hours or on high for 3–4 hours, stirring occasionally if you're home (though it's not essential). The potatoes should be tender and the sauce should be creamy and bubbling around the edges when done.

Once the crockpot dish is finished cooking, taste it and adjust seasoning if needed—add a few dashes of hot sauce if you like a little kick, or more salt and pepper to your preference. Sprinkle the fresh parsley over the top just before serving for a pop of color and a hint of brightness against the rich, creamy dish. Serve directly from the crockpot or transfer to a serving dish.