Does "add in X" mean to "put X in something", not "put something into X"?

Native speaker’s answer
Rebecca
Yes, that's correct! To "add in X" means to put X into something. Thus, "add in the wet [ingredients]" here can be understood as "put in the wet [ingredients]" into the mixture. You can understand "add in" as meaning "put [in]" or "include [in]." Ex: I'd like to add in some extra materials for our project. Ex: Once you've added in the butter, you can put in the rest of the ingredients.