The Irish-, British- and Australian-English phrase I’m talking, or I’m speaking, to the butcher, not to the, or his, block is used when, while addressing someone, the speaker is interrupted by someone else—in particular when the person who interrupts is a subordinate of the person whom the speaker addresses.

(In this phrase, block designates the piece of wood on which a butcher chops his meat.)

The earliest occurrence of the phrase that I have found is from “Weekly Nation” Joke Competitions, published in The Weekly Nation (Dublin, County Dublin, Ireland) of Saturday 20^th August 1898—the phrase seems to have already been well established, because it occurs in a joke involving a butcher and his assistant, and because both the words butcher and block are in inverted commas:

The following is a selection of jokes sent in for last week’s competitions:—
[…]
IN HIS PLACE.
An old woman in Lancashire a short time ago purchased a piece of beef from a butcher’s shop. It did not turn out to her expectations. So next time she went to the shop, she began giving the butcher a piece of her mind. Just in the thick of the squabble the assistant turned round and says to the old woman: “You know very well you had that beef three-pence a pound cheaper.” Whereupon the old woman turned on him with a contemptible look, and said: “One at a time, please. I’m talking to the ‘butcher,’ not to the ‘block.’”
Miss M Lonergan, Screhan, Windgap, Co Kilkenny.

The second-earliest occurrence that I have found is from The West Australian (Perth, Western Australia) of Tuesday 4^th February 1913:

City Baths.—At a special meeting of the Perth City Council held last night the question of raising a loan for, amongst other works, the construction of city baths at the Hyde Park lake, was taken into consideration. The amount that it was proposed to allocate for the purpose was £9,000. […] Several of the councillors pointed out that it was futile to allocate so large an amount of loan money for the work when it yet remained to be proved whether water was obtainable, and whether, if so, such water would be cool enough to be used, without cooling treatment, by bathers. They counselled caution, being rather desirous of first ascertaining whether the thing could be carried into effect before the city borrowed more money than it required. […] One councillor, who had arrived late, contended that the amount had on a previous occasion been passed, and on being interrupted by a fellow councillor, retorted “I am speaking to the butcher, and not to the block,” which retort raised general laughter.

The phrase then occurs in Football Notes, by ‘Goal Post’, published in The Daily News (Perth, Western Australia) of Friday 1^st September 1916:

Does the League exercise any supervision with regard to the appointment of timekeepers? It should do so if only to prevent a recurrence of the disgraceful incident, which occurred in the members’ grandstand at W.A.C.A. Ground last Saturday. Instead of giving all their attention to the business in hand the timekeepers in the third quarter started an argument about the respective merits of certain players. The East Fremantle timekeeper became very assertive. Soon his voice could be heard all over the grandstand. Someone advised the noisy timekeeper to be quiet, and was rewarded with the witty (?) remark, “I was talking to the butcher not to the block.”

The following is a British-English use of the phrase—from “Mail” Mems, published in The Daily Mail (Hull, Yorkshire, England) of Wednesday 17^th April 1929:

Mr J. W. Bentley, when he was interrupted at the meeting of the Sculcoates * (Hull) Guardians, on Tuesday, remarked to his interrupters that he was “speaking to the butcher and not to his block!”

(* Sculcoates is in the East Riding of Yorkshire.)