In a mixing bowl, combine 1 cup of self-raising flour with 5 ounces of sweetened Greek yogurt. Mix until it forms a soft, pliable dough. Knead gently for 1-2 minutes.

Divide the dough into equal portions and roll each into a log about 1-inch thick. Cut into small pieces and roll each piece into a ball.

Preheat your air fryer to 350°F (180°C) for about 5 minutes. Lightly oil the air fryer basket.

Dip each doughnut ball into melted butter and place in a single layer in the basket. Cook for approximately 5-6 minutes until puffed and golden brown.

While still warm, prepare the cinnamon sugar by combining granulated sugar and ground cinnamon. Dip in melted butter and roll in the cinnamon sugar.

Serve warm, drizzling with melted chocolate if desired.