Got this recipe years ago and have been using it for years.  Best pork tenderloin I've ever had and everybody that tries it loves it.  Thought it was time to share:

As a public service to my trusted allies I'm sharing this recipe. It is badass. Never fails. Always impresses. It's a little bit of a pain in the ass to source the two main marinade ingredients (in TN) but worth the trouble.  Emphasis added below because I've had friends try to shortcut the ingredients and it sucks when you do.

Ingredients:

1 package containing 2 pork TENDERloins. NO, not LOINS

1 entire head of Elephant Garlic
NO, NOT REGULAR GARLIC

8-12 ounces of DARK soy sauce.  NO, NOT REGULAR SOY SAUCE

1 entire stick of butter. Whatever kind of butter.  Butter is butter.

Look around and find the right ingredients. Don't be trying to substitute the wrong ingredients for my awesome, badass recipe.

Rough chop/slice the entire freakin head of elephant garlic. Not 1 clove-the entire package.  Doesn't have to be chopped too fine. That's a US quarter for comparison.


Sauté (sweat) the garlic in the melted stick of butter. Add the dark soy and stir well. Don't go getting all freaky and try to use regular soy sauce. Your dog or pet goat won't be able to choke this stuff down if you screw up and buy regular soy sauce or try to use regular garlic. Let marinade cool.

Lay the two tenderloins out, pierce them all over with a fork and rub with some black pepper. It ain't rocket science just use whatever amount you're comfortable with.

Pour the mixed up marinade on top in a baking dish, plastic container or my personal favorite a 2 1/2 gallon zip lock bag. Turn to cover the meat.

Stick in the fridge for 2 1/2 to 3 hours. Not 2. Not 5. I like to rotate or turn the tenderloins every half hour to hour. The fridge is that big 6 foot tall box in your wife's room that you keep your beer in. It's usually white or silver in color.  Ask her if in doubt. Also if she's one of those really good wives that not only makes the sandwiches but fetches your beers don't admit you know of said fridge's existence.  Marinate the meat in a cooler in the backyard with some ice.

After 2-1/2 to 3 hours take your meat out (hahahaha) and let it get closer to room temp. I let it sit out for half an hour which is coincidentally about how long it takes charcoal to burn down after lighting and get right for cooking.  
Can't help you if you have gas (hahahaha again). Get rid of that gas grille.  
 
Toss on the grill over some grey coals or low to medium heat if you still haven't tossed out that pathetic gas grille.  I toss a hickory chunk on the fire at this point.  The marinade is a mighty bold flavor so the bold hickory smoke makes it even better.  Pecan or cherry don't cut it.

Close the lid with the vents open and slow grill the suckers until they are MEDIUM.  Turn them every 4 or 5 minutes. That would be 145 degrees for anybody sophisticated enough to own an instant read thermometer. If you don't have one, quit being a cheap, amateurish schmuck and order one. Your friends and loved ones will think you've become a grilling God.  

Warning: it will smell like a barnyard the first five or ten minutes it's cooking due to all that butter burning.  

Halfway there. Note the lack of flames and charred flesh:

You want them to have a little pink in the middle. 145 is minimum cooked temp for pork and the max you want to cook this dish. I cook to 138 and let them sit covered ten minutes.  They rise to 143 to 145.

If you've ignored my sage thermometer advice and insist on being a cheap and amateurish then eyeball them and try to determine that they're done by picking them up from one end with tongs. When they just start to stiffen up and don't bend easily they're getting right. Ask your wife if in doubt whether the meat's stiff enough.  Bet you get a wisecrack.
 
After 20 minutes at 325-350 degrees according to the 49 cent thermometer on the grill:

You know deep down that grill thermometer is a no-good, lying piece of crap, but it makes you feel better THINKING it's 325 degrees inside the grill. The reality is it's roughly somewhere between 215 and 499 degrees in there, give or take a few.

Let them sit 10-15 minutes covered with foil after they hit 135-140 (the temp will climb while they're resting) then slice into medallions about 1/2" thick. They can sit for 30 minutes and that just makes them juicier and better. Hide the knives because all you need to cut the medallions up and eat them is a fork.

Done:

Congratulations. Everybody you cook this for will bow down and praise you. Also you will definitely need some French bread to sop up the ungodly juices on the platter after you have sliced this up. In fact you can probably just toss out the meat and sop up the juice and call that dinner.

Try it and let me know what you think.

I'd bet I could make this with regular soys sauce and garlic powder, and in a blind taste test you would not be able to pick out yours from mine.

Forge ahead. Good luck. I bet if you actually cook it you will change your mind.

I've had several people try what you suggest and it was fairly terrible.

There's reasons for the specific ingredients but good luck amigo.

Thank you, OP.
I tried this recipe yesterday, followed it exactly and got great results! It's a keeper for sure! I'm lucky in that elephant garlic is grown local and easy to get, dark soy sauce is easy to get here too. After making this dish, I see why regular soy sauce and garlic would ruin it.
A couple of pics...

Glad you tried it and enjoyed it!  Hope others will too.

Gonna tag this one.

Don't know where in the he'll I'll find elephant garlic or dark soy in this one horse town, but I'll start looking.

Amazon

 

Send me a pm and a package might show up to get you started.  

Looks mighty fine

Looks good. There's plenty of Asian markets around here, so shouldn't be a problem sourcing the ingredients.

Damn, good on you OP

Definitely giving this a shot. Thanks!

Will elephant garlic be with regular garlic at the grocery or is that something to look for at an Asian market?  Tag for trying.

My Albertson's have elephant garlic hanging out with the normal garlic. Along with shallots and other aromatics.

In Left Tennessee Kroger often has it. If not the manager can get it in stock.

Taggin this one.



OP, just curious, have you tried completing this in a smoker?  Its a little slower cooking on the lower temp.  250-275.

oops

Nope.

Tenderloin is lean with zero fat in the muscle.  I don't think there's anything to gain by low and slow.  Like cooking a beef filet or tenderloin.  Might do the reverse sear on the smoker then fire it up on coals to finish.  It's so juicy and tender I never saw any need to not just grill it though.

Did your soy sauce expire in November of 2014?

Tag for later.


Probably gonna try this one.

Hey.  I never said I JUST took the pictures.  I did this originally for some coworkers a couple of years ago.  Been through a couple of gallons since then.

Hah, I figured. I went and got some dark soy sauce last night to try this recipe out.

Let us know how it goes!

If you don't like it I'll give you double your money back.

I think I'll give this a try, looks good.

My favorite way to do pork tenderloin is balsamic vinegar (a LOT, the cheap stuff is fine) and rosemary. Brown the meat in an oven proof pan, take it out, add the balsamic vinegar and reduce to fairly thick consistency, enough to coat the pork in a glaze. Roll pork in glaze, throw in rosemary, cover, and toss in oven until finished.

Also, that's no shit about the thermometer . Everything I cook is nice and juicy, how do I do it???

Rat,

I did this today.  Absolutely incredible.  My girlfriend loves it!!!!!


My only deviation was that I used a pellet grill and all I had was pecan pellets at the time.  


Very very good.


Thanks!!!!!!!

I wanted to like but lost it at the ultra.

Glad you tried it and really glad you like it!

That's why it's the last, lone beer in the fridge- nobody wanted it.

 
I was going to ask about a pellet grill.  Thanks for the update.

Made it a few days  ago and it was damn good! I did make some changes to the whole process though. I couldn't find any dark soy sauce so I just made a copycat recipe of 1-4c water, 1c brown sugar, and 3/4 cup soy sauce. I first cooked the garlic with the butter, then added the water and brown sugar to the garlic and butter. I let that come to a boil until it thickened. Once it was at the consistency I liked I added the soy sauce and cooked for a bit more. I let it cool and threw it into a ziplock with the tenderloins. And I ended up letting it marinate for a full 24hrs and it turned out out fantastic.

Cool.  That sounds great.

Try the original sometime and compare.  The beauty is the simplicity and how little time it takes.

The flavor profile is amazing as well as how tender and juicy the medallions are.  Probably can order the ingredients online.

Made this last night and it was amazing.  I ended up turning it into sliders.

Sweet!  Glad you tried it and liked it.  That is my favorite way to eat it.  I toss two slices on a slider bun and sometimes add a little good BBQ sauce (even though it doesn't need it).

Thanks for letting us know you liked it!

Not a true dinner pic, but have to give back.

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Well, welcome to the Cooking forum, me!
I didn't even know this existed. I love to cook.
I intend to try this forthwith.