-- For a half batch, use half the ingredients and bake in an 8 inch square pan.
-- If eggs are room temperature, you won't have to beat (whisk) them quite as hard to mix them with the other ingredients and will probably end up whisking less air into the batter. In my experience, whisking or stirring ingredients rather than beating them usually makes a denser, less cakey, bar. these are not cakey at all.