Wash Jerusalem artichoke, boil until tender in plenty of salted water, about 30 minutes.
Drain the water, cool the Jerusalem artichoke, dry, peel and cut into slices.
Put in a salad bowl, season with oil, sprinkle with lemon juice. Salt, pepper and mix.
Cut the bacon into thin slices and fry in a pan until crispy cracklings form. Take out, put on a paper towel, let drain excess fat.
Cut the bread into small cubes and brown in the remaining fat from the bacon. Put the fried croutons on a paper towel to drain excess fat. Add croutons and cracklings to a salad bowl with Jerusalem artichoke. Mix well and sprinkle with green onions.