In blender, pulse parsley, basil, cilantro, mint, garlic, and lemon juice with ½ cup of olive oil. Set aside. The sauce can be made ahead of time and stored in refrigerator in airtight container.
Cut off cauliflower stems, then place heads cut-side down and slice into 1-inch-thick slices. You should have about 8 slices.
While cauliflower is boiling, in small bowl, whisk ½ cup olive oil, red pepper chili flakes, and whole grain mustard.
Grill cauliflower for 3-4 minutes on each side until golden brown.
Serve 2 cauliflowers per plate, and garnish with truffle oil or salt and green herb sauce, and side of cooked quinoa.