Preheat the oven to 220C/450F/Gas 7. Grease a six-hole muffin tin with vegetable oil using a pastry brush.
Beat the egg together with the milk in a jug until well combined. Add the honey, vanilla extract and orange zest and beat again.
Put the flour into a mixing bowl and make a well in the centre. Pour in half of the egg mixture, gradually bringing the edges of the flour into the wet mixture with a fork until the mixture is smooth and thoroughly combined.
Pour over the remaining egg mixture and mix again with the fork to form a smooth, runny batter.
Divide the blueberries equally among the six holes in the muffin tray. Spoon in the batter (about three tablespoons of batter per hole).
Bake the muffins in the oven for 10-15 minutes, or until they have risen and are golden-brown, and a skewer inserted into the centre of each comes out clean.
Set aside to cool slightly, then remove the muffins from the tray and set aside to cool on a wire rack. These are delicious eaten as they are, or served with plain yoghurt.