How soft is your butter? Are you melting it first? Some people do that so it is easier to incorporate into the other ingredients not realizing it goes though a chemical change (omg I used the ef-word in baking chemical
But umm where was I, melted butter turns into butter fat, some milk solids and some water so you have a much different composition to work with. If we do this we are adding water to our cookie dough and it's just not the same.
But I mean whatever fat you use even if it's shortening should not be melted.
Cookie making thoughts about melting moments.