1. Heat the olive oil in a large saucepan over medium heat. Add the chopped onion and minced garlic, and cook until softened, about 5 minutes.
2. Stir in the cocoa powder, ground cinnamon, ground cumin, dried oregano, and salt. Cook for another 2 minutes, stirring constantly.
3. Add the vegetable broth, crushed tomatoes, peanut butter, raisins, and sesame seeds. Stir well to combine.
4. Bring the mixture to a boil, then reduce the heat to low and simmer for 45 minutes, stirring occasionally.
5. Remove from heat and let cool slightly. Transfer the mixture to a blender and blend until smooth.
6. Return the sauce to the saucepan and heat through before serving.