Cut the white onions into ½ cm thick rings; halve the red onions, then cut into ½ cm thick slices. Separate into individual rings and slices. Trim the spring onions, but leave whole.
To make the batter, sift the flour into a bowl and whisk in enough of the lager to form a smooth coating batter. Season with salt and pepper to taste.
Heat about an 8 cm depth of oil in an electric