Cook bacon and shallots in a large skillet. Remove to a paper towel-lined plate. Pour off bacon grease.
Parboil potatoes until tender on the outside, but still raw on the inside. Let cool, then grate. Add to a bowl and mix with salt. Mix in cooked bacon and shallot.
Melt half the butter with half the olive oil in the skillet. Add the potato mixture. Spread evenly in the pan and lightly press with your fingers. Cook ten minutes, or until golden and crispy.
Place a plate on top of the skillet and flip the skillet over so rosti falls onto plate. Melt the remaining butter with the olive oil in the skillet. Slide rosti back into skillet, and cook a further ten minutes.
Remove rosti to a plate. Cut into wedges. Serve with smoked salmon, crème fraiche, and sprinkle with chopped chives.