Why egg white makes a sour foam: dry shake, reverse dry shake and aquafaba

An egg white turns a sour silky and gives it a foam head, but only if you shake it right. This piece explains what the white does, then walks you step by step through the dry shake and the reverse dry shake, with an aquafaba version for no egg.

The trick is one hard shake with ice for the chill and one without ice for the foam. Step through each method, scale the spec for a crowd in ml or oz, and read the food-safety note on raw egg.