Start by peeling and chopping both the Large Russet and Yukon Gold potatoes into even-sized chunks. Place them in a large pot, cover with cold water, and add a generous pinch of kosher salt. Bring the water to a rolling boil over medium-high heat, and allow the potatoes to cook for 15-20 minutes, or until fork-tender. Drain the potatoes well and set aside.

Return the drained potatoes to the pot over low heat. Add in the unsalted butter and heavy cream, then use a potato masher or ricer to mash until smooth and creamy. Stir continuously until well combined, keeping the mixture warm.

In a large skillet, melt a tablespoon of unsalted butter over medium heat. Add the chopped medium onion and sauté for about 5 minutes, stirring frequently, until softened and translucent.

To the skillet with the sautéed onion, add the chopped green cabbage. Reduce heat to medium-low and cook for 7-8 minutes, stirring occasionally, until the cabbage is tender and lightly browned.

Gently fold the sautéed onion and cabbage into the creamy mashed potatoes in the pot. Incorporate half of the crispy cooked bacon into the mixture, mixing until evenly distributed. Season your Irish Colcannon with kosher salt and fresh ground black pepper to taste.

Transfer the Irish Colcannon into a serving bowl and top with the remaining crispy bacon. For an extra touch of indulgence, add a pat of butter on top while serving.