pousse café/chasse café

brandy or liqueur, or a mixture or layering of them

Began as a French tradition, by the 1780s, of a brandy or liqueur served after the meal; by the 1850s, the bourgeoning class of professional bartenders in America transformed it into a “stunt drink” that showed their mastery of their ingredients and technique

The pousse café, champerelle, and chasse café—all names for the same basic idea—have a great many “recipes”, but the key is actually the specific gravity of each component, which determines which will layer must go above or below another. Generally speaking, the higher the sugar content, the heavier the ingredient. If you search the internet for “specific gravity of liqueurs”, you will find quite a few reference tables to work with. The examples in the above image are from Jerry Thomas’ 1862 book. Here’s another:

Parisian Pousse Café

Carefully layer, in order, in a liqueur glass:

2/5 orange curaçao
2/5 kirschwasser
1/5 green Chartreuse

Oxford Companion to Spirits and Cocktails, p. 555–6; barware icons courtesy of Haus Alpenz