Preheat oven to 350°F. Coat a 9- X 9-inch glass baking dish with cooking spray.

In a food processor, combine gingersnaps, butter and 2 tablespoons milk; process until completely blended.
Spoon mixture into prepared baking dish and press down crust with fingers to form a crust.
Bake crust for 10 minutes; remove from oven and let crust cool for 20 minutes.
Reduce oven to 325°F.

Meanwhile, in a large bowl, using an electric mixer, combine remaining 2 tablespoons milk, cream cheese and egg until well-blended.
Add vanilla extract, cinnamon, brown sugar and pumpkin; blend until smooth.
Spoon pumpkin mixture over crust and smooth into an even layer.
Bake until center sets and a knife inserted in center of bars comes out clean, about 35 minutes.

Remove from oven and let cool.
When cool, cover and refrigerate overnight.
Cut into 12 bars and serve each with a tablespoon dollop of whipped cream.