Scrub potatoes well; prick with fork in several places. Bake at 375°F for 1 to 1 1/4 hours or until easily pierced with fork.
Meanwhile, melt 2 Tablespoons butter in small saucepan. Saute onion and green pepper until tender.
When potatoes are cool enough to handle, remove thin slice from top of each potato. Scoop out inside of potato, leaving 1/4 inch thick shell. Place potato pulp in mixing bowl with remaining 2 Tablespoons butter. Beat, adding enough milk to make stiff mashed potato mixture. Add Worcestershire sauce, corned beef, onion, green pepper, and butter in which they were cooked; mix well. Add salt and pepper to taste. Fill potato shells with mixture, make a well in top of each potato. Bake at 350°F for 30 minutes.
Meanwhile, combine water and 1 teaspoon salt in medium saucepan; bring to boil. Add vinegar to boiling water. Break eggs, 1 at a time, into sauce dish; slide into boiling water. Poach eggs to desired degree of doneness.
Place 1 poached egg in well on top of each potato. Garnish with parsley. Serve. Makes 4 servings.
NOTE: The stuffed potatoes can be prepared a day in advance and refrigerated until baking time. Allow a few extra minutes to heat.