In a large saucepan, boil the meat seasoned with salt and onion in plenty of water until tender. How long it takes depends on the cut of meat. You can shorten this process in half by using a pressure cooker. Reserve the stock for the stew.
Cut both ends off the plantains with a sharp knife for easier peeling. Make a shallow cut lengthwise along the seam, cutting just into the peel. Remove the peel by pulling it away.
Slice the plantains into 2-3 pieces, depending on their size. If not using immediately, cover with cool water.
Chop the tomatoes, onions, and green onions, and place them in a food processor or blender. Add njansa, peeled pebe, garlic, basil, parsley, and celery. Add a little bit of water if using a blender to facilitate blending. Blend until pureed.
Heat up a large pot with oil, then add the tomato mixture, white pepper, curry powder, meat, and the reserved stock. Bring to a boil, reduce the heat, and simmer for about 10 minutes, stirring occasionally.
Then add the plantains, bouillon or Maggi, and enough stock or water to cover the plantains. Continue simmering until the plantains are super tender (an hour or more). Add water as necessary to prevent burning.
Adjust seasonings to taste, and serve hot.