Fry the porcini mushrooms in a non-stick pan in olive oil until golden. Then take it out and set it aside.
Fry the garlic and onion in the pan until the color turns slightly brown. Then fry the olives briefly. Now add the balsamic vinegar and let it simmer a little more (about 3-4 minutes).
Pour the dressing over the porcini mushrooms and season with salt and pepper. Cool and let steep for 1 hour.
When the salad has cooled down, fold in the plucked basil leaves. Possibly drizzle a little olive oil over it (to taste).