1 leek, white and light-green part cut into 1/4-in. rings
3 tbsp olive oil
1 head garlic, cut in half cross-wise
3/4 cup 35% cream
3/4 cup parmesan, divided
2 tbsp white balsamic vinegar
2 tbsp grainy mustard
2 tbsp fresh thyme
1/2 tsp salt, divided
450-g penne rigate pasta
YIELD 4 servings
PREHEAT oven to 400F. Toss cauliflower, cut into bite-sized pieces, with leek, white and light-green part cut into 1/4-in. rings, and olive oil on a large baking sheet. Cut garlic in half cross-wise. Rub cut sides of garlic on excess oil on baking sheet, then wrap in foil. Place wrapped garlic on the side of sheet. Bake in centre of oven, flipping halfway through, until cauliflower edges are golden, about 30 min.
STIR cream with parmesan, white balsamic vinegar, grainy mustard, fresh thyme leaves and 1/4 tsp salt in a medium bowl. Set aside.
COOK penne rigate in a large pot of boiling water following package directions, but omitting salt, until tender, 6 to 8 min. Drain, then return to pot. Squeeze and mash garlic into cream mixture, then stir into pasta until coated. Stir in roasted vegetables and remaining 1/4 tsp salt. Divide pasta among 4 plates and sprinkle with 1/4 cup parmesan.