Heat the oven to 400ºF. Scrub the potatoes clean, pat dry, and pierce in several places with a fork. Set on an oven rack and bake until very tender when pierced with a fork, about 1 hour. Let them cool completely on a wire rack.Put the bacon in large skillet and cook over medium heat, stirring occasionally, until browned and crisp, 8 to 10 minutes. Remove the bacon bits with a slotted spoon to a plate lined with 2 thickness of paper towel and let drain. Leave about a tablespon of bacon fat in the skillet.

Add the butter to the skillet over medium-low heat and let melt; stir into the bacon fat in the skillet. Add the leeks, season with salt, and cook, stirring occasionally, until softened, about 10 minutes. Set aside a couple of tablespoons of the sautéed leeks for garnish. Add the garlic and cook for an additional minute or two.

Add the broth and water; heat to a simmer and cook until the leeks are tender, about 15 minutes.

When the potatoes are cool, cut them in half lengthwise. Scoop the flesh out of the skin in one piece from each half. Cut the potato into 1/2-inch cubes and set aside.

Coarsely chop the potato skin and add them plus any loose pieces of potato to the pot with the leeks. Purée the contents of the pot until very smooth using an immersion blender (See Notes about countertop blender). Return the puréed soup to the pot and reheat over medium low.

Whisk together the milk and sour cream until smooth, add to the soup with 1/2 cup of the Mexican Blend cheese; whisking everything together until the cheese melts.

If the soup seems too thick, thin it with a little water. Add the cubed potato and stir gently to combine; season to taste with salt and pepper.

Garnish with the sour cream, Mexican Cheese, sautéed leeks, and bacon bits.