Pan-Grilled Asparagus and Oyster Mushrooms with Pancetta and Garlic Puree

Asparagus and mushrooms are particularly good cooked slowly on a heated iron grill, or a la plancha—a method that imbues these vegetables with a clean, pure taste and concentrates their flavors. For best results, I cook each vegetable in its own way, arranged side by side on a grill set over two burners, until tender and charred, then combine them just before serving.

I lightly salt half the grill before setting the asparagus on top, and I lightly oil the other half and sprea