Preheat oven to 180 degrees celsius (fan-forced). Lightly grease 1 x 12 hole muffin tin with cooking oil spray. Cut each pastry sheet into 6 squares and press into the muffin holes. Set aside.
Place the parmesan cheese into the TM bowl and grate for 5 - 10 seconds on Speed 8. Set aside.
Place the onion into the TM bowl. Chop for 5 seconds on Speed 8. Scrape down the sides of the bowl and repeat.
Add the olive oil and saute for 4 minutes on 100 degrees, Speed 2.
Place the thawed frozen spinach into a strainer and remove any excess liquid (the more liquid you can remove, the crispier your pastries will be).
Add the spinach, ricotta cheese and parmesan cheese to the TM bowl. Season with salt and pepper. Mix for 20 seconds on Reverse Speed 5, or until completely combined.
Divide the mixture evenly between the pastry cases.
Brush the whisked egg over the pastry.
Cook in the oven for approximately 20 minutes or until golden and crispy.
Allow to cool for 5 minutes in the tray before transferring to a wire rack to cool completely.