Colcannon is often made with ham or bacon and cabbage or other greens that have been sautéed in butter, and then mixed into mashed potatoes, with a well of melted butter on top. But leftover Corned Beef and Cabbage is so flavorful against the mild mashed potatoes, and with browned butter to boot you may agree with me that the Colcannon you have for lunch the next day is really the reason to make Corned Beef and Cabbage.
So here’s the strategy, formula, and technique. The proportions are more or less, give or take. Make what you need:
Make your browned butter: In a large pot, slowly melt 1 – 2 T butter per serving and cook over low heat until solids brown, but not burned, and have a nice nutty smell. Pour into a small bowl, but don’t clean the pot as you’ll be using it for your potatoes (that’s why you want a large pot and not a small saucepan).
Cook your potatoes: You’ll need some freshly mashed potatoes for this, so bake, microwave, or boil however many potatoes you’ll need, one or two per serving. I prefer to bake or microwave them. When they’re soft, rice, sieve, or mash potatoes into the brown butter pot. Add some warmed milk (or buttermilk, whey, half and half, or cream) and a very small amount of butter. I like to keep it light on the fat and salt, to balance the high fat and salt in the corned beef and browned butter. Pepper potatoes. Keep warm
Warm leftover corned beef in microwave or oven. Shred it by pressing slices along the grain with the side of a knife. Chop shreds into ½” – 1” pieces.
Warm leftover cabbage and onions.
Per serving stir a few tablespoons of warm corned beef , a few tablespoons of warm cabbage and a teaspoon or so of minced parsley into mashed potatoes, reserving some to be served on the side. Make sure this potato mixture is good and hot.
To serve, mound piping hot potatoes into a bowl and place warm corned beef, warm cabbage, and minced parsley around the edges. Make a well in the center of the potatoes and fill with browned butter.