meatpork
I've seen both boneless pork sirloin chops and pork sirloin roasts in the grocery store, for different prices.
From their names, I would think the chop is intended for grilling and the roast is intended for roasting, but if they're both cut from the sirloin, what's the difference between them besides the shape?
The term "double" is not specific to pork - it's also used with lamb - but it means something different in each case.
A lamb double chop or loin double chop differs from a regular loin chop by including both the top loin and tenderloin, but not the flank. It hasn't actually been cut twice.
A pork butterfly chop is sometimes called a "double chop" because, as the name implies, it's been butterflied. A very thick cut is taken from the loin eye and then cut again to make the butterfly.
Of course, if you cut a butterflied pork chop in half, and served just one half, it would basically be a regular pork chop. So if you that's what you actually got, I'd call it a marketing gimmick.
I've never actually heard the term "double-cut chop" - there are some vague references to it on Google, but as far as I know, it's not a proper butchering term. Perhaps the term got relayed through several people and mutated somewhere along the way.
I don't know the whole algorithm, but I found the formula you'd need to derive it.
First, as you said, you would need a reference for the final internal temperature of the meat. McGee On Food And Cooking is a good source, I don't know of any online accessible ones, although they probably exist.
Second, you have to calculate the time needed to reach that temperature. The system of equations you need is (assuming a simple case - I am sure that adding oil to the pan, or breading the meat, or using a microwave will all change it a lot):
No, I don't know what these variables stand for. The book from which I scanned this uses it as an example why asking for such an algorithm is pointless. I guess you could look it up in the paper cited below the equations, if you are so inclined. I will stick with my thermometer.
Best Answer
You've answered your own question, it's size and shape. You could buy a roast and slice it into chops and you'd get the same thing as if the butcher does it. That's if they are both pork sirloin, sometimes there can be confusion between sirloin and tenderloin, which are not the same thing.