Solution

The sets of ingredients in the puzzle are the same ingredients used in different recipes in Ingredients with one extra.

Food	Ingredients used	Leftover
Seafood Tartare	Blood Orange, Lobster, Sea Bass, Olive Oil	Cod
Chocolate Mousse	Chocolate, Lemon, Butter	Honey
Pumpkin Velouté	Pumpkin, Black Truffle	Eggplant
Eel Matelote	Eel, Bay Leaf, Parsley	Scallop
Consommé	Celery, Onion, Cloves	Saffron

The first letter of each unused ingredient spells the solution.

CHESS