Rinse and drain the rice. In a large pot bring the water, bouillon, rice, and two pinches of salt to a boil. Cook until the rice is tender.

In a small bowl, mix the yogurt, milk or buttermilk, egg yolk, and flour until combined. Take a few spoonfuls of the hot liquid from the pot and incorporate into the yogurt mixture. Slowly add the yogurt mixture to the pot while stirring continuously. Cook for an additional 10 minutes.

Melt the butter in a small skillet and add the dried mint. Cook and stir until fragrant. Add the butter mixture to the soup pot or place a spoonful as topping to each bowl.