Add soda water to get the consistency you want and stir it in. If I’ve managed to get my stick blender out, I don’t use it for this bit – I just use a fork or a whisk. Start slow, because it’s tricky to explain just how much will make your batter the thickness that you want – I generally find that about 3/4 of a cup gets it to where I want to be – not too thick, not too runny. Once it’s all mixed in it should have lots of lovely bubbles on top. You can skip this and just add extra milk if you want, but I find the soda water makes the pancakes so light and fluffy!