Preheat oven to 325° F. and spray an 8x8 square baking pan with cooking spray. 

In a food processor, pulse the graham crackers into fine crumbs. Add in the brown sugar, cinnamon, ginger and salt and pulse until combined. Pour in the melted butter and pulse until combined. Dump the mixture into the prepared baking pan and spread into an even layer. Use the bottom of a measuring cup to firmly press the crumb mixture into the bottom and sides of the pan. Bake for 12-14 minutes or until lightly golden. Cool for several minutes before pouring in the pumpkin filling.

While the crust bakes, wipe out the bowl of the food processor then add in the Greek yogurt, pumpkin, brown sugar, eggs and vanilla. Purée until smooth. Scrape down the sides of the bowl with a rubber spatula, then add in the pumpkin pie spice, cinnamon, salt and cornstarch. Purée again until everything is incorporated and smooth. Pour the filling over the baked graham cracker crust and tap the pan a couple times on the counter to get out any air bubbles. Bake on the middle rack of the oven for 35-45 minutes or until the center jiggles just slightly when you shake the pan. 

Cool the bars to room temperature before refrigerating for at least 2 hours. Serve the bars topped with whipped cream and cinnamon.