Bklynm123, while I would hope that your butcher has at least a rudimentary knowledge of the Halachos pertaining to the preparation of kosher meat, you’re probably better off getting your instructions from your Rav.
I’m not sure I know what your butcher was talking about.
And I’m quite sure he didn’t know what he was talking about.
But I would add that with regard to taste and texture, not laws of Kashrus, I would not mix ground meats with ground liver in cooking.