Prepare saffron water by placing 1/4 teaspoon of saffron in a small dish and melting an ice cube over it. Set aside for later use.

Heat vegetable oil in a large pot over medium-high heat. Add chopped onion and cook until translucent (about 5 minutes). Brown the chicken pieces for 7-10 minutes on each side.

Stir in minced garlic and cook for an additional minute. Add spices and mix well before incorporating tomato paste, half the saffron water, and chicken stock.

Reduce heat to low and simmer uncovered for about 4 hours, stirring occasionally until the meat is fork-tender.

Rinse basmati rice under cold water and cook according to package instructions, about 15-20 minutes.

Melt butter in a small pan over low heat, then add barberries with a pinch of sugar and sauté for 1-2 minutes.

Combine 1/2 cup of cooked rice with sautéed barberries and reserved saffron water, mixing well.

In a mixing bowl, combine diced cucumber, tomatoes, and red onion with lemon juice and mint. Season with salt and pepper, and chill.