Rinse blueberries, dry well and coat in 2 tablespoons of flour.
Cream the butter with the sugar. Add the egg and flour, stir in cocoa powder, salt, baking powder, baking soda and yogurt. Stir until all ingredients are combined. Stir in the floured blueberries and mix gently.
Preheat the oven to 200°C (approximately 400°F). Line a muffin tin with paper baking cups, and divide the batter equally. Bake in the oven approximately 30 minutes. Remove from the oven and let cool.
Serve, dusted with powdered sugar.