If the ricotta you buy looks watery, drain through a fine mesh strainer. Also, if you don't have a tart pan, you can use a baking sheet, following the directions below. Prep: 20 minutes, Bake: 20 minutes.
Preheat oven to 350°. Unfold 1 pastry sheet, pinching seams together if necessary, and place into 10-inch square tart pan, trimming if needed for fit. Brush with egg wash.
Cut 4 (1/2- x 10-inch) strips from remaining sheet, and lightly press across each side of egg-washed pastry to create borders; brush border with egg wash. Prick bottom sheet all over with fork. Sprinkle half of the Parmesan cheese over bottom; place tart on lower rack of oven. Bake at 350° for 5 to 8 minutes or until cheese forms a light crust. Let cool for 5 minutes.
Combine ricotta and next 5 ingredients. Spoon about two-thirds ricotta mixture into pastry shell, and spread evenly.
Sauté spinach in a large skillet over medium heat for 2 to 3 minutes, stirring often and cooking in batches if necessary; drain excess liquid. Add spinach evenly onto ricotta mixture in pastry shell, and dollop remaining ricotta mixture onto spinach. Sprinkle with remaining Parmesan, and bake at 350° for 15 to 18 minutes or until set.
*You can substitute 1 (10-ounce) package frozen chopped spinach, cooked and drained, for the fresh spinach, if desired.