Preheat oven to 160 celsius (320 fahrenheit) and grease and line a 22cm x 8cm loaf tin with baking paper. Place the butter in a small saucepan over a medium low heat along with the tea leaves and stir until melted. Set aside for 20 minutes to infuse. Strain the butter through a fine mesh sieve and discard the tea leaves.
Place all the ingredients except the blueberries in a bowl and stir well to combine. Add the blueberries and mix through carefully. Pour the mixture into the prepared loaf tin and bake for 1 hour, or until the cake is cooked and a skewer inserted into the middle of the cake comes out cleanly. Dust with icing (confectioners) sugar and top with extra blueberries to serve.