Peel and dice 2 medium potatoes and 1 large carrot. Finely chop 1 medium onion.

In a large pot or Dutch oven, melt 2 tablespoons of unsalted butter over medium heat. Add the diced onion and cook until softened, about 3-5 minutes.

Add the diced potatoes and carrot to the pot. Stir and cook for another 5 minutes.

Pour in 4 cups of good quality chicken or vegetable broth, enough to cover the vegetables. Add 1 teaspoon of dried thyme, 1/2 teaspoon salt, and 1/4 teaspoon of black pepper.

Bring the mixture to a boil, then reduce the heat to low, cover, and simmer for 20 minutes or until the vegetables are very tender.

Remove from the heat and mash some of the vegetables with a potato masher or fork to thicken the stew slightly. Alternatively, for a smoother consistency, you can use an immersion blender.

Stir in 1 cup of chopped cooked corned beef (or leftover roast beef) if using, and 1/4 cup of chopped fresh parsley. Heat through if needed.

Serve hot, garnished with a sprig of fresh parsley. A dollop of sour cream or a slice of brown soda bread are great accompaniments.