Wash the potatoes and cook for about 20 minutes. Quench, peel and let cool. Cut avocados in half, remove seeds. Peel avocado halves, cut into pieces and sprinkle with lemon juice.
Cut the potatoes into slices. Clean and wash the salad and cut into strips, except for 4 leaves. Wash the tomatoes and remove the stalk. Dice tomatoes. Clean, wash and slice the mushrooms.
Heat the fat in a pan and fry the mushrooms in it. Season with salt and pepper. Remove the mushrooms and deglaze the frying fat with the vinegar. Wash the herbs, chop finely and add to the vinegar. Stir in oil and season with salt and pepper.
Pour the marinade over the salad ingredients. Line a bowl with the lettuce leaves and arrange the loosely mixed salad on top.