Preheat the oven to 450ºF (230ºC). Line a baking sheet with parchment paper.

Remove the leaves from the cauliflower and cut off enough of the stem so that it is level with the bottom of the head, enabling the cauliflower to stand upright on the baking sheet.

Gently stuff the garlic slivers between the florets all around the cauliflower head.

Whisk together the olive oil, 2 tablespoons of the mustard, the honey, and the vinegar in a small bowl and season to taste with salt and pepper.

Put the cauliflower on the prepared baking sheet and brush the entire outside and inside with the olive oil mixture. Roast the cauliflower until beautifully browned and tender, 50 minutes to 1 hour. You can insert a long skewer into the cauliflower to see if it’s done. It should pass through smoothly. Keep the oven on.

Meanwhile, combine the parsley and feta in a small bowl. Brush the remaining 2 tablespoons mustard all over the surface of the roasted cauliflower and rub with the parsley-feta mixture. Roast for 5 minutes more, or until the feta melts. Remove from the oven and serve with lemon wedges.