গন্ধরাজ লেবু / Gondhoraj Lebu / King Lime.
I think that's the secret.
I visited Kolkata during Dasara / Durga Pujo last year and was amazed by the culture and food scene. Bit unfortunate that majority of it was inaccessible to vegetarian me, but there were still plenty of unique choices for me to try.
I was very interested in trying Fuchka or Puchka - Bengal's version of India's ever popular Pani Puri or Golgappe. I've always liked this snack (sans the terrible hygiene maintained by most Pani Puri vendors) so was curious to know what the difference - if anything - was.
I liked it. A lot.
The whole Fuchka experience was fun. The masala is made custom for you every time, the vendors always ask if you need extra green chillies or masala powder. I don't really know all the details of it, but there's one thing I do know, and it's that the paani / water / "jol" is different.
There was something about it, very appealing and interesting but couldn't quite put my finger on it, but there quite sure was something. If it was sweetnees, spice, or sourness, I would probably have been able to figure it out but there was something else in the water. Something different.
Upon "investigating" it further, I think I know what the secret is - it's Gondhoraj Lemon.
What I noticed over the course of my 2 week stay was that this breed of lemon was used everywhere in Kolkata. Much more so than normal lemon that rest of India is used to.
Gondho = Fragrance. Raj = King.
Quite literally, King of Fragrance.
These are slightly larger in size, and longer / cylindrical of sorts in shape. They're cut vertically into 4, instead of the typical halves.
The taste is milder and less acidic in nature, but the entire point of this citrus fruit is the fragrance.
I'd describe it to be quite similar to Kaffir Lime. If I could describe that smell, it's fresh, floral, and uplifting. It's divine. It's royal. It feeeels good.
So in Fuchka Jol, and all other street food, they use this lime over normal round basic ones. It's not really a strong fragrance in that water but it just adds a bit of something in there. It's cut up into pieces and thrown into the Fuchka water.
If you want to experience the full potential of this, you gotto try their version of Buttermilk + Lassi combo called "Gondhoraj Ghol". The zest of Gondhoraj is added to the curd + sugar + salt + limejuice combo and it's straight up heavenly!
Disclaimer: I'm not Bengali nor have I grown up eating Bengali food. This is just an observation.
I've been able to find these in Bangalore recently. Do try and let me know!