Place a large pot of water over high heat and allow it to come to a boil while preparing other ingredients.

Place a heavy, well-seasoned cast-iron skillet over low heat and allow the butter to melt slowly in it while you dice your onions. You want the pieces of onion to be no larger than 1/4". Lob the root end off of the carrot. Slice it in half crosswise, then lengthwise. Lay the carrot quarters cut sides down on your cutting board and slice into 1/4" thick strips lengthwise. Turn the strips perpendicular to your knife and chop roughly into 1/4" cubes. When the butter is fully melted, add the carrots and onions to the pan, sprinkle with a pinch of salt, then stir. Raise the heat to medium low and let cook while dealing with the potatoes then corned beef, stirring occasionally to prevent scorching. The carrots and onions should cook for about 8-10 minutes.

To dice the potatoes, first slice them in half lengthwise. Lay, cut side down, on the cutting board and cut into 1/4" thick 'cards'. Lay a stack of the potato 'cards' on the cutting board, cut sides down, and slice into 1/4" strips. Turn the strips perpendicular to your knife and chop roughly into 1/4" cubes.

Salt the now boiling water with a hearty pinch of kosher salt and carefully add the diced potatoes. Return to a simmer. The potatoes should be mostly tender within 3-5 minutes. Do not cook them until they're mushy. Drain and set aside.

To dice the corned beef, cut across the grain into 1/4" thick slices. Stack the slices and cut into 1/4" strips. Turn the strips perpendicular to your knife and chop roughly into 1/4" cubes.

By this time, your carrots and onions should have softened and the onions should be beginning to turn golden around the edges (at the 8-10 minute mark.) Turn the heat to medium. Add the boiled potatoes and diced corned beef to the pan and toss to evenly distribute the onions, carrot, potatoes, corned beef and fat. If it looks dry, you can add a little more butter or canola oil. Use a sturdy metal spatula or wooden spoon to press the mixture down toward the bottom of the pan. This promotes more caramelized bits and goodies. Grind black pepper over the mixture, to taste.

Do not stir at this point!

If you hear sizzling and popping you are on the right track. If you don't hear it, raise the heat a bit and see if that sets the sizzling in motion. If you still don't hear good things happening, add a bit more fat (either butter or canola oil), and that should do it. After about 5-8 minutes, when things start smelling toasty, slide a metal spatula under the hash and lift a bit to examine the progress. If it is starting to get golden brown bits, use your spatula to slide underneath and flip over the hash in sections. Don't stir it, or you'll break up all those lovely crisp parts. Press the hash down again to bring more surface area in contact with the pan. This is how you achieve the best coloring and texture on the hash. Cook for about 5 minutes, then lift and flip sections again. Carry on doing this until you get the degree of caramelization you prefer. When it is the color you desire, remove the pan from the heat. Cast-iron retains heat, so if you do not want it to cook any further, you should transfer it to a serving dish immediately.

Serve hot.

I prefer mine with stir-fried kimchi and a fried egg on top, but most of my kids love it straight up with hot sauce. Leftovers can be stored in a tightly covered container in the refrigerator and reheated in a skillet or in the microwave.