Step 1
Place racks in center and decrease third of oven; preheat to 350°. Toast ½ cup blanched hazelnuts on a rimmed baking sheet, tossing as soon as, till golden brown, 8–10 minutes. Let cool, then coarsely chop; put aside. Improve oven temperature to 375°.
Step 2
Generously coat 2 giant rimmed baking sheets with extra-virgin olive oil. Minimize 1 giant head of savoy cabbage (about 3 lb.) in half by means of core; minimize every half into 6–8 wedges, conserving core intact.
Step 3
Toss 6 oz. Gruyère, coarsely grated (about 1½ cups), and 1 Tbsp. cornstarch in a medium bowl to mix. Convey 1⅔ cups heavy cream, 2 Tbsp. Dijon mustard, 2 garlic cloves, finely grated, 1 tsp. finely grated lemon zest, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, and 1 tsp. freshly floor pepper to a simmer in a medium saucepan. Add Gruyère combination a handful at a time, whisking after every addition till melted. Prepare dinner sauce, whisking continuously, till thick sufficient to coat a spoon, about 1 minute. Take away from warmth. Style cheese sauce and season with extra salt and/or pepper if wanted.
Step 4
Working with one wedge at a time, brush cabbage on all sides with about half of cheese sauce. Sprinkle very generously on all sides with 5 oz. Parmesan, finely grated (about 3 cups), urgent to stick. Divide wedges, minimize sides down, between ready baking sheets, spacing no less than 1″ aside.
Step 5
Roast cabbage till starting to brown on high, 30–35 minutes
(don’t fret if stray bits of cheese on baking sheet burn barely). Flip wedges over and
rotate baking sheets high to backside and entrance to again. Proceed to roast till golden
brown in spots on the opposite aspect, 20–25 minutes longer.
Step 6
In the meantime, combine ¼ cup finely chopped parsley, reserved toasted hazelnuts, and remaining ½ tsp. finely grated lemon zest in a small bowl to mix. Season with salt and pepper.
Step 7
Warmth broiler. Consolidate cabbage on one of many baking
sheets and broil on higher rack, watching carefully, till darkish brown and charred in spots,
about 3 minutes.
Step 8
When able to serve, warmth remaining cheese sauce over
medium, whisking typically and loosening with a splash or so of cream if wanted, simply till
steaming, about 2 minutes. Unfold sauce in a shallow serving dish or on a platter and
organize cabbage wedges on high. Scatter parsley combination over, then high with extra
Parmesan.
