Remove the rind from the black bread and cut the slices into cubes. Fry them in a tablespoon of butter until crispy. Let cool on kitchen paper.
Heat the olive oil and butter. Place the sprig of thyme in the pan. Fry the sliced porcini mushrooms in it. Remove from the pan, season with salt and pepper and keep warm in the oven at 60 °. At the same time fry the bacon cut into narrow strips in a dry pan until crispy. Deglaze the mushroom pan with the balsamic vinegar and add the remaining ingredients for the vinaigrette.
Nap the salad with the dressing and serve with the mushrooms, bacon and croutons.