2 1/2cupscooked corned beeffinely diced (or 340g/12oz can corned beef)
Salt and freshly ground pepper
3Tbspdried bread crumbsor 1/4 cup fresh bread crumbs
Make the Mashed Potatoes: Add peeled, cut potatoes (evenly sized) to a large pot of cold water. Add salt to the water. Bring to a boil over high heat and cook until potatoes are tender, 10-20 minutes, depending on the size of the potatoes.
Meanwhile, heat milk and butter in a small saucepan over low heat until warm, then keep warm until needed.
Drain then return potatoes to dry pot. Place over medium heat on the stove top. Add milk/butter mixture to the pot. Mash potatoes until smooth. *Add a bit more milk, if needed. Taste and add salt and freshly ground pepper, to taste. Cover and set aside (or cover and refrigerate if making ahead).
Preheat the oven to 400F.
Make the Filling: Heat 2 Tbsp butter in a large skillet over medium heat. Add the onions and cook until softened and starting to turn golden a bit. Add the Worcestershire, ketchup, chicken broth, parsley and thyme to the skillet. Simmer over medium heat until liquid reduces by half. Add the corned beef and reduce heat slightly. Simmer 3-4 minutes or until there is only a bit of liquid left in the mixture (don't let all of it cook off). Taste the mixture and add additional salt and freshly ground pepper, as needed.
Spoon filling into a small baking dish (8-inch round-ish). Spoon mashed potatoes over-top in an even layer. Top with shredded cheese, then sprinkle with bread crumbs.
Bake in preheated oven for about 30 minutes, or until filling is heated through and bubbling and top is lovely and golden.
Be sure to read the Cook's Notes above the Recipe Card, where I share some valuable tips, options, substitutions and variations for this recipe!