Place the potatoes in a large pot with water to cover over high heat. Bring to a boil and cook until the potatoes are tender. Remove from heat, drain, combine with the milk and 3/4 of the butter, mash and set aside.
Melt the remaining butter in a large frypan over medium high heat. Saute the bacon, onion and garlic in the butter for 5 to 10 minutes, or until the bacon is fully cooked.
Cook the lasagne according to packet directions and cool under running water.
Place 1/2 of the mashed potatoes into the bottom of a 20x30cm baking dish. Top this with 1/3 of the cheese followed by a layer of lasagne. Repeat this with the remaining potatoes, another 1/3 of the cheese and a layer of lasagne. Arrange the bacon, onion and garlic over the lasagne, then another layer of lasagne and finally top all with the remaining cheese. Season with salt and pepper to taste.
Bake, uncovered, at 180 degrees C for 30 to 45 minutes, or until the cheese is melted and bubbly. Serve with sour cream and chopped fresh chives.