In a large pan sauté meat for about 10 minutes on 3 tablespoons of peanut oil until lightly browned on all sides. Stir constantly to keep from burning. Set aside.
In the pressure cooker pot sauté onion on 1 tablespoon of oil for about 3 - 4 minutes. Stir in the garlic and ginger, sauté for 1 - 2 minutes.
Add the meat to the pot, stir in the tomato concentrate and chopped tomatoes; bring to a boil. Reduce flame and simmer for 8 - 10 minutes to reduce the volume of the tomatoes.
Add enough beef stock to loosen the dish to a stew like consistency.
Stir in the eggplant, peanut butter and cayenne pepper.
Cover and lock lid on pressure cooker. Bring to pressure and, when pressure is reached, turn the flame down to low. Continue cooking for 10 minutes. Turn off the flame and release the pressure naturally.
Serve stew with rice or couscous.
Easy variations: mafé becomes a full meal by adding vegetables like cabbage, yams, squash, okra, eggplant, potatoes, peppers or carrots. For vegetarian mafé eliminate the meat and use only vegetables.