Cut off both ends of each green banana. Using a sharp knife, make a slit down the length of the peel, then peel away the skin.
Immediately place the peeled bananas in a bowl or pot of cold salted water. (see note 1 below).
Cut the bananas into to 3-inch (7.5 cm) chunks. Set aside.
Heat the cooking oil in a large pot. Add the beef and brown on all sides.
Stir in the onion and cook for 3-4 minutes until softened. Add the garlic and cook for another minute.
Add the diced tomatoes, tomato paste, paprika, salt, and black pepper. Pour in about ⅓ cup water if the pot feels too dry, then stir well.
Cover and cook for 8-10 minutes, or until the tomatoes have softened.
Pour in 1 cup of water, cover, and simmer for about 30 minutes, or until the beef is tender. If the beef is still tough, add a little more water and continue cooking until tender.
Add the remaining 1½ cups of water, followed by the green banana chunks. Stir gently to coat them in the sauce.
Cover and cook for 15-20 minutes, or until the bananas are tender. They should be soft enough to pierce easily with a fork but still hold their shape.
Taste and adjust the seasoning with more salt and black pepper if needed. If you prefer a thinner sauce, stir in a little more water until it reaches your desired consistency.
Garnish with freshly chopped coriander and serve warm.