Drain and rinse both the soaked chickpeas and fava beans under cold running water to remove any debris.
In a large pot, combine the rinsed fava beans with enough fresh water to cover them. Add the cumin and a pinch of salt. Bring to a rolling boil, then reduce the heat and simmer for about 90 minutes, or until the beans are tender.
While the fava beans are cooking, prepare the flavored base. In another large pot, heat the olive oil over medium heat. Add the garlic, chili peppers, tomato paste, harissa paste, saffron, paprika, and turmeric. Cook for a minute or two to release the aromatics' fragrances.
Stir in the lemon juice, diced tomatoes, and the soaked, rinsed chickpeas. Add enough water to cover the ingredients. Mix well to blend the flavors. Bring to a boil, then reduce the heat, cover, and simmer for about 45-60 minutes, or until the chickpeas are tender. Check occasionally and add more water if necessary.
Once the fava beans are cooked, drain them and add to the pot with the chickpeas. Stir to combine and adjust the seasoning with salt and pepper.
Cook the mixture together for an additional 10-15 minutes, allowing the flavors to meld.
Garnish with fresh spring onions and chopped parsley before serving.