If at this stage you are able to mix it into a rollable cookie dough, so what you have is a proper cookie dough instead of a crumbly dough, then you may not need to add any soy milk, but if you have crumbly dough, then you need the soy milk. This usually depends on the moisture content of your brand of vegan butter and/or peanut butter so you can just judge this by eye. I used Flora Dairy Free and Proper Nutty and I did add all the milk.