Recipes should be costed out to be a single serving not a full recipe.  Therefore, you don't need to change the yield and per serving data, we automatically default to 1 serving.  This is important because if you are connecting it with your sales data you want 1 sold item to equal the ingredients for 1 serving.

However, if you are creating a sub-recipe it can be a full recipe with yield and serving size.  You will then use that recipe in another recipe either by serving size or another amount.