Wash the unpeeled potatoes and cut them in half lengthwise, then in half again. Boil the potatoes in lightly salted water for 20-25 minutes.
Meanwhile, wilt the spinach.
Fry the onion, garlic, and stewing steak in a little olive oil until the meat is light brown.
Add the potatoes and mushrooms and fry for 2 to 3 minutes. Season to taste with salt and pepper. Stir in the spinach, serve in a salad bowl and garnish with roasted pine nuts.