Start by peeling and dicing your russet potatoes into 1 1/2-inch chunks. This size ensures that they'll cook evenly. Place the diced potatoes in a large pot and cover them with cold water. Add a pinch of salt. Bring it to a boil over high heat.

Once boiling, reduce the heat to a simmer. Cook for about 15-20 minutes or until the potatoes are fork-tender. You should be able to poke a piece easily. Drain the potatoes and let them sit in the pot for a few minutes to let off some steam.

While the potatoes are cooking, chop your greens. Whether you choose kale, cabbage, or Swiss chard, make sure they are finely chopped. While the potatoes are still warm, they will mix better with the greens.

Return the drained potatoes to the pot. Add in the butter, and let it melt over the warm potatoes. Then add the whole milk or heavy cream. Use a potato masher to mash them until smooth but still a little chunky, keeping some texture.

Fold in the chopped greens and green onions. Mix well until the greens have wilted slightly from the heat. Then, sprinkle in the garlic powder and drizzle the fresh lemon juice over the mixture. Adjust salt to your taste.

Want to make it fancy? Serve with additional pats of butter on top, or even a sprinkle of fresh herbs if you're feeling adventurous. Enjoy your steaming bowl of colcannon!