Whole Roasted Cauliflower with Green Herb Sauce

Preheat oven to 450 degrees. Place cauliflower on a parchment-lined rimmed baking sheet. Brush with 1/4 cup oil; season with salt and pepper. Pull short sides of parchment over cauliflower and fold one end over other a few times to seal. Fold long ends of parchment under cauliflower to create a packet. Roast until knife-tender, about 40 minutes. Tear open parchment at top; roast until golden brown, 15 to 20 minutes more.

Stir together parsley, cilantro, garlic, mustard, vinegar, and remaining 1/2 cup oil in a small bowl to combine. Season with salt and pepper. Serve cauliflower warm, with sauce alongside.