Peel and finely chop the onion. Cut bacon into strips. Roast hazelnut leaves in a pan without fat until golden brown and remove. Put bacon into the hot pan and let it crisp. Add the onions and sauté briefly and remove from the heat. Add 1 tablespoon of water and vinegar and season with coloured pepper and a little salt. Stir in the oil and let it cool down a bit.
Clean and wash the salad and drain well. Pluck oak leaf lettuce into bite-sized pieces, cut romaine lettuce into strips. Mix salad and vinaigrette and arrange on plates. Sprinkle with hazelnut leaves. Slice the parmesan curls over them at the end. Serve immediately. Serve with baguette