Heat oil, add garlic and cumin and fry a couple minutes (until golden brown). Add fava beans, stir well and cover with water. Cook for about 10min or more over low heat until beans are soft, adding more water as needed. Transfer to bowl, mash into thick paste. Season with salt, pepper and lemon. Then add chopped herbs and a bit more olive oil. Finally stir in caramelised onions, reserving a few to sprinkle on top.