Lovely variant on a Negroni though I agree with John McTague the Suze can be overwhelming and have reduced it even more. So: 1.5 parts Gin, 1 part Lillet, 0.5 parts Gentian. I used the "mild" Bombay Sapphire Gin which needed the kick of 2 drops of celery bitters and 3 drops of grapefruit bitters (in lieu of fresh zest) - these transformed the drink miraculously. I felt like a Medieval alchemist! Otherwise, use Plymouth or the specified Celery Gin. Lovely drink!

Absolutely love this cocktail, in equal parts. I used Gordon's London dry gin, from which the juniper forward taste combines very well with the bittersweet notes of Suze and Lillet.

Made my first with Tanqueray, Salers, and Cocchi Americano. Deliciously bitter, earthy, and interesting! Thank you for the recipe!

I made this today with Botanist gin, Salers gentian (red cap) and Lillet Blanc. I was not entirely happy with the results. The interplay of the Salers and Lillet sud not wirk out for my taste - I was missing some of the bracing bitterness I expect from a drink with Negroni in the name. I might tinker with the proportions a bit, or try the Negroni Bianco with Luxardo Bianco Bitters. Suze might make a difference but is currently unavailable in Virginia.

Had to substitute Kina for Suze, and it was wonderful!

After first tasting without, I found the grapefruit zest absolutely necessary. For my taste Suze dominates the taste a bit too much (not because of the bitterness). I will reduce it next time to ¾ oz.

I'm about to add a variant of this recipe that was available at a now defunct restaurant called Prospect, on Fulton St in Fort Greene, Brooklyn: called the Polka Dot (cool name!), it uses blanc vermouth instead of lillet and (convenient) grapefruit bitters instead of the grapefruit garnish, and a garnish of luxardo cherry

I swapped out the Lillet for Mancino Sakura Vermouth and also found that even with Lillet that a lemon zest twist, expressed,
instead of grapefruit really elevates the drink.