In a large pot, add the diced potatoes and cover with a couple of inches of water. Bring to a boil, then reduce to simmer, allowing the potatoes to cook for about 15 minutes, or until a knife is easily inserted and potatoes are tender. Drain, return cooked potatoes to the pot, and allow to steam for about 5 minutes.

In a medium skillet, add the pancetta and cook until crispy, about 5 - 8 minutes, or until golden brown. Drain the cooked pancetta on a paper towel-lined plate. Set aside.

Mash potatoes in the pot, add the garlic, sage, and butter. Then add in the milk and cheese, mashing and mixing well until creamy.

Add in all but a couple of tablespoons of the crispy pancetta and mix well. Season with salt and pepper, to taste. If needed add a little more milk, a tablespoon at a time, until you have the desired consistency.

Serve garnished with the remaining pancetta, and if desired any of the pancetta drippings, a small grating of more cheese if desired and a sprig of fresh sage.