Preheat the oven to 190°C, 375°F, Gas Mark 5. Put 10 paper muffin cases into a muffin tin.
Mix together the two cheeses on a plate. Sift the flour, baking powder, salt and sugar into a large mixing bowl. Stir in about three-quarters of the cheese and all the chives (if using).
Beat together the egg, milk and vegetable oil in a separate bowl. Add to the dry ingredients, stirring until just combined. It is very important not to overmix the ingredients - the batter will be quite lumpy but there should be no dry flour visible.
Spoon the mixture into the muffin cases, then sprinkle the reserved cheese on top. Transfer to the oven and bake for 20 - 25 minutes until light golden brown. Cool for a few minutes, then serve whilst warm.