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1
Place the oven rack in the center of the oven.
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2
Put a large rimmed baking sheet on the rack, and preheat the oven to 500 degrees.
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3
Prepare one 12-inch sheet of foil and spread flat on the counter-top.
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4
Set the garlic heads, cut-side up, in the center of foil.
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5
Drizzle 1/2 teaspoon oil over each head and seal the packet.
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6
Put the packet on the oven rack and roast until the garlic is very tender, 38 to 42 minutes.
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7
Open the packet and set aside to let cool.
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8
While the garlic is roasting, trim the outer leaves of cauliflower and cut the stem flush with the bottom.
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9
Cut the head from pole to pole into 8 equal wedges.
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10
Add the cauliflower in a large bowl along with 1 1/2 tablespoons oil, 1 teaspoon salt, blqck pepper to taste, 1 pinch of sugar, and toss until well coated and mixed.
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11
Remove the baking sheet from the oven.
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12
Carefully transfer the cauliflower to the hot baking sheet and spread into even layer, arranging cut side down.
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13
Bring the baking sheet back to the oven and roast until cauliflower is well browned and tender, 24 to 28 minutes.
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14
Transfer the roasted cauliflower to the cutting board.
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15
When cool enough to handle, chop into 1/2-inch pieces.
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16
While cauliflower roasts, bring 4 quarts water to a boil in a large pot.
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17
Stir in the pasta and about 1 tablespoon salt, and cook until ad dente.
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18
Squeeze roasted garlic cloves from their skins into a small bowl.
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19
With a fork, mash garlic to smooth paste, then mix in red pepper flakes and lemon juice to taste.
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20
Slowly whisk in remaining 1 1/2 tablespoons of oil.
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21
Drain pasta, reserving 1 cup cooking water, and return pasta to pot.
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22
Stir in chopped cauliflower, pasta and garlic sauce, 4 tablespoons of the cooking water, parsley, and extra lemon juice to taste.
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23
Sprinkle remaining cheese and toasted walnuts on top.
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24
Serve right away.
