In a large saucepan, add the peeled and chopped Russet and Yukon Gold potatoes. Cover with lightly salted water and bring to a boil. Reduce heat and simmer for 15-20 minutes, or until fork-tender. Drain and set aside.

Return the drained potatoes to the pot and mix in unsalted butter and heavy cream or whole milk. Mash until creamy and smooth.

In a skillet, melt butter over medium heat. Sauté the chopped onion for about 5 minutes until tender and translucent.

Add the chopped green cabbage to the skillet and cook for about 7-8 minutes until tender and lightly browned.

Fold in the sautéed onion and cabbage mixture to the mashed potatoes. Add half of the crispy bacon and season with salt and pepper to taste.

Transfer the Colcannon to a serving bowl, top with remaining bacon pieces and a pat of butter.