In a large pot, bring 3 cups of water to a boil.
Slowly add the pounded yam flour to the boiling water, stirring constantly to prevent lumps from forming.
Reduce the heat to medium-low and continue stirring until the mixture becomes smooth and thick.
Remove the pot from the heat and set it aside to cool slightly.
In a separate pan, toast the egusi seeds over medium heat until they are lightly browned and fragrant.
Grind the toasted egusi seeds into a fine powder using a spice grinder or food processor.
In a separate pan, heat the palm oil over medium heat.
Add the diced onion, minced garlic, and habanero pepper (if using) to the pan and sauté until the onions are translucent.
Add the ground egusi, ground crayfish, diced tomato, and beef broth to the pan and stir to combine.
Bring the mixture to a boil, then reduce the heat to low and simmer for 10-15 minutes.
If using, add the chopped spinach or kale to the pan and stir until it is wilted.
Season the soup with salt and pepper to taste.