Which of the following sauces is made by clarifying butter?

The correct answer is brown butter sauce. This sauce is created by heating butter to the point where the water evaporates, and the milk solids settle at the bottom. The butter eventually browns due to the Maillard reaction, which imparts a rich, nutty flavor. This technique of clarifying the butter is an essential step in making brown butter sauce, distinguishing it from other sauces.

Mornay sauce, a variation of béchamel, incorporates cheese but does not involve clarifying butter. Beurre blanc is a classic French sauce made from butter, white wine, and shallots, typically emulsified rather than clarified. Gremolata is a fresh condiment made from lemon zest, garlic, and parsley, and doesn’t involve any butter preparation. Thus, brown butter sauce stands out as the correct answer due to its reliance on the clarification and browning process of the butter.