In my experience, sweetbreads are one of the hardest offal to deal with. Heart is pretty consistent, brains no problem, livers are liver, and pretty much everything else is pretty consistent. Sweetbreads however are always different. No matter what supplier your getting them from or how much your paying your only guarantee is that they will be different everytime even the same batch will have its inconsistencies. For me its the most intimidating offal of them all to get right. And when they're right, they're great.
We've tried everything, soaking in milk, butter milk, purging, brining, paoching to all different consistencies, peeling before, after, filleting, pressing, smoking, sauteing, frying, braising, sous vide...flour, cornstarch, flour and cornstarch....the list goes on.
nothings ever consistent enough to make me happy but we deal with them the best we can.
Sometimes they are so tense and chewy and other times they are creamier then brains.
Our technique as of today is we get them in, we begin the soaking process of multiple changes of water, a night in milk for good luck, a rinse and then a 4 hour brine in salt and water.
We used to poach in bouillon, but found the mirepoix flavor too strong, so then we poached in just milk. Better, but still inconsistent because of poaching temps and human error. We then tried Hestons sous vide directions.....67 degrees i think for like two hours... what a load of crock... maybe they eat sweetbreads like that in the UK, but not here in my kitchen.
So we toyed around and concluded that for 30-35 minutes at 59.5 degree's sous vide gives us the best results.
Now, unlike a pork belly, your not going to get the same results time after time. Most cookbooks dont tell you about all the possible things that one should take into consideration or all the possible things that could go wrong. Every things usually written in stone leaving only the "season to taste" up to the cook. So regarding the sweetbreads, use common sense. Sweetbreads come in all different sizes from both the heart and neck cuts. Sometimes they are mangled holding on to eachother with just a bit of membrane, other times they're beautiful plump apple cuts. They may seize up after cooking or they may relax. And sometimes they may be so tense onced cooked you could bounce them off the wall!
Divide them by size in your vac pac bags. Smaller the piece, shorter the cooking time. Large lobes should be broken down where they naturally seperate while keeping they're integrity. These will take longer. Even when sous vide, these fuckers are inconsistent, so i wish you the best of luck.
Onced cooked , shock them in ice water.
Remove from bag and press between two sheet trays. Its important to put a good amount of weight on them. This process is not just to remove blood and moisture from the sweetbreads but also to break down the protein structure so that when you fry or sear them they dont seize and curl up like squid or cuttlefish. Once pressed, the sweets should be relaxed and the outer membrane should be easier to remove.
Some sweets have insane veins running through them that are really strong and will be chewy as hell is you leave them in. Something we've been doing recently is to fillet them like a chicken breast and remove the main vein that runs through them.
The filleting technique is not really mentioned anywhere in books or on the net and yet i think it is one of the most important steps. Sure you can try and pull it out from one end but goodluck in getting it all.
Once filleted, cook as you wish. Our frying time has been reduced my 3/4 of the time we used to now that we sous vide and fillet. Just enough to warm through and develop a nice light crust. As always, new techniques and findings will continue to arise with this amazing but inconsistent delicacy.
Like a steak, let your sweets rest for a minute before they make it out to the table.