In a large pot add the olive oil and flour and stir over medium low heat for 1 - 2 minutes.
Add the yogurt and stir till it is all incorporated, then keep on stirring for another 1 - 2 minutes.
Start adding the milk and water slowly and stirring after each addition till they are well incorporated and there are no lumps. Add the bouillon cubes and stir till dissolved.
When the soup reaches a slow boil, finely crush the mint leaves between the palms of your hands and add to the soup and stir. Add salt and pepper to taste.
You can serve it with some heavy cream in each bowl (optional)