UK foods I miss...
You have Kinder Eggs. They are *illegal* here.
You have Ribena - you can't get *any* kind of squash here.
You have ice-cream vans if you can catch them, actual real tea that isn't some strange herbal infusion, decent curry, bread that isn't some kind of over-sugared travesty, kebabs, brown sauce, proper pancakes that aren't some kind of flat sponge, savoury French fried bread, Bird’s custard (sorry Americans, you have custard all wrong), pasties, sausage rolls, Jaffa Cakes, Penguins, fizzy cola bottles, Code D'Or chocolate, HP sauce, Cadbury's Flakes, Worchestershire Sauce, christmas pudding, mince pies, lamb (can apparently be had, but I’ve rarely seen it here), fruit gums and jelly babies, Galaxy Caramel, lemon curd, Scotch eggs, Crunchie bars, curried mackerel (I miss this so much!), cheese & onion crisps, Marmite, mint Aeros, haggis, Turkish delight, Branston Pickle, Yorkshire puddings, Golden Syrup for making flapjacks (no *not* those pancakey things!), Bounty bars, instant gravy, crumpets, Bulmer's or Gaymer's perry, decent rashers of bacon instead of the 50% fat streaky things they have here, fish and chips that isn't made from a sandal-sole, toilet paper that's the right shape, any chocolate or cheese worthy of the name, digestives, HOBNOBS OH MY GOD I WOULD KILL FOR A DECENT HOBNOB IT DOESN'T EVEN HAVE TO HAVE CHOCOLATE ON I JUST WANT SOMETHING I CAN DUNK WITHOUT IT FALLING APART!
The good news is, I have since found a Hobnob supply (HEB supermarket has a nice “international foods” section). Also good supplies of many of the others, which I’ve italicized above. So if anyone’s in Texas and want to know where to find those things, just ask! And if you know where to find curried mackerel I’ll love you forever.
But yes, the difference in US cookies vs UK biscuits simply cannot be guessed without understanding that they are aimed at entirely different ways of consuming them. The majority of biscuits bought in the UK will be eaten with a hit drink, and will be dunked.
This is not like the idea of drinking Oreos with cold milk. People tell me it’s the same thing, which demonstrates they simply don’t get it. They don’t understand the physics. Doing that gets you an Oreo, which is wet with milk. That is NOTHING like a dunked biscuit, not in taste, not in effect, not in chemistry, and not in physics. It’s an entirely different animal. A much sadder animal.
The Australians get it: the Tim Tam Slam is exactly the right idea, except it lacks the engineering rigidity. Which, I admit, is sort of the point of the Tim Tam Slam.
But anyway, the fact that we dunk every biscuit we eat in the UK means that the biscuit making bakeries — or more correctly, factories — put every single batch through many dozens of tests to make sure that they dunk correctly. So you get the dunkable digestive biscuits, rich tea biscuits, custard creams, jammie dodgers, shortbread, gingernuts, bourbons, jaffa cakes… all of which Americans have complained to me are too hard, or too dry, because they aren’t eating them the way they are intended.
A non-dunk-optimized cookie will either fail to soak up the drink and to use the hot liquid to carry the flavor to your receptors, and stay crunchy, or it will just collapse into a soggy heap, usually as you lift it out of the cup, so that a chunk falls into the cup and splashes everywhere, and the rest falls down your front.
In contrast, the Chocolate Hobnob is an engineering masterpiece, the pinnacle of British culinary engineering and science. There is no other biscuit quite like it.
Eaten alone, it’s an oat cookie with chocolate on. A granola cookie with a layer of chocolate, if you will. It’s pretty nice. Not too dry. Tasty.
But once you dunk it, then the magic begins. The sugars that hold the grains together melt onto your tongue, loosening the grains so that it falls apart in your mouth but the size of the grains prevents it from falling apart in your cup or your hand (a common problem with lesser cookies). The chocolate melts into a velvet molten delight, and as with the sugars, the hot water carries them to your tastebuds and into the air in your nose so you can taste them so much better. It’s the perfect balance between cohesion and crumble. It’s a masterpiece.