How to Make It
Preheat the oven to 400°. Spread the hazelnuts on a large rimmed baking sheet. Bake for 8 to 10 minutes, until fragrant and lightly browned. Transfer the hazelnuts to a kitchen towel and rub together in the towel to release the skins. Let the hazelnuts cool, then coarsely chop. Leave the oven on.
On the large rimmed baking sheet, toss the squash with the olive oil and coriander and season with salt and pepper. Roast for about 20 minutes, turning once, until tender and browned in spots. Let cool.
Meanwhile, in a small bowl, whisk the buttermilk with the mayonnaise, garlic and 2 teaspoons of pepper. Season generously with salt.
On a large platter, toss half of the escarole with half of the arugula. Scatter half each of the squash, hazelnuts and pomegranate seeds on top. Repeat the layering one more time. Serve, passing the buttermilk drizzle at the table.