Butternut Squash With Pistou without soup

1 sheet of frozen puff pastry, thawed (from a 17.3-ounce package) 1 large egg beaten with 1 teaspoon water 12 1/8"-thick rounds peeled butternut squash kosher[...]

3 1/2 pounds butternut squash (about 2 medium), peeled, seeded, cut into 3/4- to 1-inch cubes (8 cups) 2 tablespoons olive oil Coarse kosher salt 4[...]