Cook the wheat in water or broth until soft for about 1 hour.
Mix the yogurt with the water and sour cream. Whisk the egg with the flour and place in a saucepan. Heat slowly and pour in the yogurt mixture. Bring to the boil, stirring constantly. Add the pre-cooked wheat and simmer for another ten minutes. A few minutes before the boil is finished, add the chopped mint or coriander. Season to taste with salt.
Either serve warm or in summer as a cooled variant.
By the way, Matsun is a special Armenian yogurt subspecies with a sour taste.