Knickerbein

The Police Gazette Bartenders Guide by Richard K. Fox (1888, p.31) — 1888

1. Layer the vanilla cordial, egg yolk, Benedictine, and kummel in a sherry wine-glass, keeping the colors separate.
2. Add two drops of bitters and serve.

Summary

A compact layered yolk-and-liqueur specialty from the theatrical after-dinner fringe.

This is useful because it preserves the tiny yolk-and-cordial display branch that sits beside, not inside, the main cocktail line.

Color separation is part of the recipe, not a decorative afterthought.

Compared with Golden Slipper, this is more explicitly pousse-cafe-like in its layering logic.

Drinks as They Are Mixed by Paul E. Lowe (1904, p.47) — Lowe 1904

1. Layer the maraschino, egg yolk, Benedictine, and kummel carefully in a bell sherry glass.
2. Add a few drops of Angostura bitters and serve.

Nose

Sweet herbal liqueur and caraway-anise notes dominate the aroma.

Palate

Knickerbein is useful because it preserves the tiny layered yolk-and-liqueur after-dinner tradition that sits beside, rather than inside, the main cocktail line.

Finish

The finish is rich, sweet, and highly aromatic.

Summary

A compact layered after-dinner drink from the yolk-and-cordial branch.

Bartenders' Guide: How to Mix Drinks by Wehman Bros. (1912, p.38)

1. Layer the vanilla cordial, egg yolk covered with Benedictine, kummel, and bitters in a sherry wine-glass, keeping the colors separate, and serve.

El Bar Americano en España by Pedro Chicote (1927, p.127)

1. Layer carefully in a sherry glass so the ingredients do not mix.
2. Serve with straws.

Garnish: Straws

Cocktails by Pedro Chicote (1928, p.318) — Knickerbein

1. Layer carefully in a sherry glass without mixing the components.
2. Serve with straws.

This matters because it keeps the Knickerbein line visible in the Spanish late-1920s after-dinner field.

The source's point is the intact yolk and the unmixed cordial stack.