Put the chicken stock, butter, salt and pepper in a large pan and bring to a boil.
Add the rice, turn the heat down and simmer for 20 minutes, or until the rice is very tender.
In a large bowl, mix the yogurt, flour and egg yolks thoroughly. U
sing a large ladle, slowly add the hot stock mixture to the yogurt mixture—stirring constantly to prevent the egg yolks and flour from clumping. After adding 4 to 5 ladles of stock, pour the mixture back into the soup and stir carefully. Simmer for another 10 minutes, stirring occasionally.
Prepare the garnish by melting the butter in a small pan over low heat and stirring in the paprika until it starts to sizzle. Ladle the soup into individual serving bowls and drizzle with the butter-paprika mixture. Sprinkle generous amounts of mint over each and serve immediately.