Given the task definition and input, reply with output. In this task, you have to identify the named entities (NER) which are the ingredients required given its directions. Named entities are the names of the items without their quantity.

Mix dry ingredients together in top of double boiler. Beat egg with milk; slowly add to dry ingredients, blending thoroughly. Cook over hot water until it begins to thicken, about 5 to 8 minutes, stirring constantly. Add vinegar and butter; continue cooking until thickened, about 3 to 4 minutes. Remove from heat and beat with rotary beater until smooth. Chill. Makes about 1 3/4 cups.
dry mustard, celery, flour, egg, vinegar, salt, pepper, sugar, milk, butter