Gin, Green Chartreuse, Campari, and Peychaud's—a Bijou-Negroni merger with New Orleans spice.
La Chartreuserie occupies the intersection of two drinks: the Bijou (gin, Chartreuse, sweet vermouth) and the Negroni (gin, Campari, sweet vermouth). The Bijou, which dates to the 1890s, runs on equal parts and maximum herbality. The Negroni runs on balance and smoothness. Both use gin as the base, and both are stirred spirit-forward drinks. The conflict is in what sits next to the gin.
La Chartreuserie resolves it by keeping Chartreuse as the herbal driver, replacing sweet vermouth with Campari as the bitter element, and adjusting the ratios to favor gin. This pulls the drink drier and more structured than the Bijou. It is more approachable than the Bijou and more interesting than the Negroni.
The deciding ingredient is Peychaud's bitters. Without them the drink is a ratio adjustment, a Bijou-Negroni hybrid with no character of its own. Peychaud's brings an anise note that bridges Chartreuse's herbal register and Campari's cherry bitterness. With it, the drink becomes its own thing.

Pre-batch all spirits together. Peychaud's adds herbal anise.
More sophisticated than standard Negroni. Chartreuse brings floral herbaceousness that works beautifully with Peychaud's anise. Refined aperitif drinking.
Build and stir. A merger of Bijou and Negroni traditions.
This merges Bijou (gin + Chartreuse + Campari) with Negroni structure. Peychaud's adds herbal anise. More sophisticated than either parent.