Sentence:  Fry in butter a small minced onion , rub with a tablespoonful of flour , <WSD>add</WSD> half a cup of cream , six beaten eggs , pepper , celery salt , a teaspoonful of minced chives , a dash of cayenne , and a pinch of nutmeg . 
Meaning of the word marked with <WSD> tags:  make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of