Drain the soaked fava beans and rinse them well.
In a large pot, add the fava beans and enough water to cover them by about 2 inches.
Bring to a boil, then reduce the heat and simmer for about 1.5 to 2 hours, or until the beans are tender. Skim off any foam that forms on the surface.
In a skillet, heat the vegetable oil over medium heat.
Add the finely chopped onion and sauté until golden brown, about 5-7 minutes.
Add the minced garlic and cook for another minute until fragrant.
Once the beans are tender, drain any excess water, leaving just a little bit of cooking liquid to keep the beans moist.
Add the sautéed onion and garlic to the beans.
Stir in the ground cumin, ground coriander, salt, and black pepper.
Use a masher or the back of a spoon to slightly mash some of the beans, leaving most of them whole.
Stir in the lemon juice and chopped parsley.
If using, mix in the tahini for extra creaminess.
Transfer the ful medames to a serving dish.
Top with chopped hard-boiled eggs and diced tomato, if desired.
Drizzle generously with extra virgin olive oil.
Enjoy your meal!