In a large pot, heat the palm oil over medium heat.
Add the chopped onions and sauté until translucent.
Stir in the minced garlic and cook for another minute.
Add the chopped red and green bell peppers to the pot and sauté until they soften.
Add the cubed eggplant and cook for about 5 minutes until it begins to soften.
In a blender or food processor, blend the ground Egusi seeds with a little water until it forms a smooth paste.
Add the Egusi paste to the pot and stir well to combine with the other ingredients.
Pour in the vegetable broth and stir to incorporate all the ingredients.
Add the dried thyme, ground crayfish (if using), and cayenne pepper. Stir well.
Reduce the heat to low, cover the pot, and let the soup simmer for about 30 minutes to allow the flavors to meld together.
After 30 minutes, add the chopped spinach and salt to taste. Stir well and let it cook for another 5 minutes.
Remove from heat and let the soup sit for a few minutes before serving.
Serve the Egusi soup hot with your choice of accompaniment, such as rice, fufu, or pounded yam.