How are the mushrooms prepared in "mushrooms a la grecque"?

Mushrooms a la grecque is a classic preparation method that involves marinating the mushrooms. This dish typically features mushrooms that are cooked until tender and then immersed in a marinade that often includes olive oil, vinegar, herbs, garlic, and spices. The marinating process enhances the flavor of the mushrooms, allowing them to absorb the aromatic ingredients, making them both delicious and vibrant.

In contrast, other preparation methods like sautéing, stuffing, or roasting involve different cooking techniques that do not align with the traditional preparation of mushrooms a la grecque. Sautéing would involve cooking the mushrooms quickly in a pan, while stuffing would imply filling them with a mixture, and roasting would involve cooking them in an oven until browned. Therefore, marinating is the distinctive method that characterizes mushrooms a la grecque, making it the correct choice for this question.