Blackjack double twice variation

I have come across a casino with a variation which allows the player to double a second time for the original stake. I have done many searches, and can find no information / strategy recommendations. Has anyone here come across this before?

Only on certain Spanish 21 tables. Could even double a third time.

Thanks for that. Have you ever found anywhere that discusses strategy for 2/3 doubles?

Basically it's doubling and drawing an Ace with a 9 against a 6 and doubling again and drawing another ace for a 21.
But it could go drawing a 2 on a 9 against a 6 and doubling with a 10 for a 21.
The hand ends when you hit 21 and you win automatically.
So if you are betting 2 units, and you double twice, you wind up betting 8 units.
There's double down rescue where you take back your double down bet but forfeit your original bet in Spanish 21 and surrender the hand. I don't know how that works if you've doubled twice. Not sure why'd you'd surrender your double down bet because you'll be hoping for a dealer bust anyway. But if the dealer has a 7,8,9, or 10 up and you doubled and got a lousy card, surrendering the doubled bet is a new strategy not seen in regular BJ. There's no regular 10's in Spanish 21, so you have a better chance the Dealer doesn't have a 10 in the hole.