I did a Google image search for "Dishes+Pure Butter'" and came up with a One King's Lane ad that showed the following trademark on that stoneware:
Parnall and Sons, Bristol England.
I cannot get the image to copy, and the item is no longer available.

Joanne Hudson Kitchen Design used to have reproductions; I guess she no longer sells them.

Here is a link that might be useful: A blog that discusses the transferware

On that same Joanne Hudson website that Kitchendetective linked, there is a platter that says "butter" instead of "pure butter" and is in stock. The website also sells platters that say "cheese", "margarine", and some others. You could also contact the company and ask if they are getting the platters that say "pure butter" back in stock.

Here is a link that might be useful: Butter Platter from Joanne Hudson

Kitchendetective and akchicago, thank you both so much!! I just knew my GW friends would know where to locate this pottery. :)

Amazon has it, but why is it so expensive?

Here is a link that might be useful: Pure Butter

I guess it's because it's an accurate reproduction of the Victorian versions, which, if you can find them, are about eight times as much.

And because her clients purchase La Cornue Chateau Series stoves, so what's another several hundred bucks?

I bought the "Pure Butter" platter from Joanne Hudson Basics in August of 2013. It was out of stock so I emailed them & got a nice reply that they expected more within about a month or so as their factory in England was having a kiln problem. It was expensive but I love it. I have it next to my range & put oil, salt & pepper, etc on it.