Dice the bacon and roast it. Remove from the pan and roast the sliced onion in the fat until golden, then also remove from the pan. Peel the potatoes raw and cut into fine slices (works well with the bread slicer). Add the butter to the pan and fry the potatoes until they are golden brown and crispy. Put the onions and bacon back in the pan, add the defrosted or blanched vegetables and toss everything for a few minutes.
Whisk the eggs with cheese, herbs and spices, pour over the potatoes, put a lid on and let set on a low flame for about 5 minutes.