Question

is the group of words in bold a phrase or a clause?
the chef prepared the meringue, a common dessert topping for citrus custards, by whipping eggs until stiff peaks formed.
phrase clause
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Explanation:

A clause contains a subject and a predicate (a verb and its related elements), while a phrase does not. The bolded group "until stiff peaks formed" has a subject ("stiff peaks") and a predicate ("formed" with the helping context of "until"). So it is a clause.

Answer:

clause