Extra-virgin olive oil, for greasing and drizzling
4 ounces smoked gouda cheese, cut into 4 pieces
1 10-ounce package frozen spinach, thawed and squeezed dry
2 large eggs plus 2 egg whites
1 15-ounce container part-skim ricotta cheese
2 tablespoons all-purpose flour
1/2 teaspoon freshly grated nutmeg
6 to 8 scallions, chopped
1 tablespoon grated parmesan cheese
1 teaspoon paprika
2 heads endive, sliced lengthwise
2 tablespoons chopped walnuts