An emulsion is a stable mixture of two liquids that normally do not combine. Oil and water do not mix. But shake them with a little mustard or egg yolk, and they form a creamy, uniform liquid. That is an emulsion. The mustard or egg yolk is the emulsifier. It coats the droplets of one liquid and keeps them suspended in the other. Mayonnaise, vinaigrette, hollandaise, and milk are all emulsions. The emulsion is a stable mixture. The emulsion is a sauce. The emulsion is the cook's trick.

Emulsions come in two types. An oil-in-water emulsion has oil droplets suspended in water. Milk and mayonnaise are oil-in-water emulsions. A water-in-oil emulsion has water droplets suspended in oil. Butter and margarine are water-in-oil emulsions. The type depends on the ratio of the liquids and the emulsifier. The emulsifier must be compatible with both liquids. It must have a hydrophilic end and a hydrophobic end. The hydrophilic end bonds with water. The hydrophobic end bonds with oil. The emulsifier bridges the two. The emulsion holds. The emulsion is stable.

Emulsions can break. If the emulsifier is insufficient, or the temperature is too high, or the mixture is overworked, the oil and water separate. A broken mayonnaise is a common example. The cook can sometimes save it by starting with a fresh emulsifier and slowly adding the broken mixture. The emulsion is fragile. The emulsion is a balance. The cook must be careful. The cook must be patient. The cook must be precise. The emulsion is the reward. The emulsion is the sauce. The sauce is the meal. The meal is the emulsion. The emulsion is the cook. The cook is the emulsion. The emulsion is the same. The emulsion is the kitchen. The kitchen is the emulsion.