Heat olive oil over medium heat, then add the onions and garlic (both minced and whole). Saute, stirring frequently for 5-6 minutes until onions have softened.
Add the green beans (you don't really need to thaw them), and cook for about 8-10 minutes, stirring occasionally, until beans fully cook through.
Add the diced tomatoes, salt, pepper and ground coriander, and mix. If there isn't enough sauce, add a splash of water. Reduce heat to low and simmer for another 10 minutes. Serve with pita bread and enjoy immediately, or cold!