01 - Bring a pot of salted water to a boil. Add diced potatoes and cook for 6–8 minutes, until just tender but not falling apart. Drain well and set aside.
02 - Heat butter and oil in a large skillet over medium heat. Add onions and bell pepper; sauté for 3–4 minutes until softened.
03 - Add cooked potatoes to the skillet. Cook for 5 minutes, stirring occasionally, until starting to brown.
04 - Stir in diced corned beef and thyme. Press hash into an even layer and cook undisturbed for 5–7 minutes, letting the bottom crisp. Flip sections to brown the other side for another 3–4 minutes. Season with salt and pepper to taste.
05 - Fill a saucepan with 2–3 inches of water. Add vinegar and bring to a gentle simmer.
06 - Crack each egg into a small bowl. Swirl water with a spoon and gently slide eggs in one at a time. Poach for 3–4 minutes until whites are set but yolks are runny. Remove with a slotted spoon and drain on paper towels. Season lightly with salt.
07 - Divide hash among plates, top each with a poached egg, and garnish with parsley. Serve hot sauce on the side if desired.