Prep: cut the potatoes, slice the onion, and slice the smoked sausage.
Cook potatoes: heat a large skillet over medium heat. Add oil. Add potatoes in an even layer. Season with a pinch of salt, pepper, and paprika. Cook 10–12 minutes, stirring every few minutes, until golden on the edges.
Steam to tender: add 2–3 tablespoons water and cover 3–5 minutes until fork-tender. Uncover and let moisture cook off.
Cook onions: push potatoes to the edges. Add 1 tablespoon butter to the center, then add onions with a pinch of salt. Cook 5–7 minutes until soft and lightly golden, stirring into the potatoes.
Brown sausage: push everything to the edges again. Add sausage to the center and cook 2–3 minutes without moving, then flip and cook 2 minutes more. Stir everything together.
Finish: lower heat to medium-low. Add remaining butter, garlic powder, and any optional seasonings. If using fresh garlic, stir it in for 30 seconds at the end. Taste and adjust salt and pepper.
Serve: garnish with parsley and serve hot.