Spray 2 (24 count) mini muffin trays with nonstick cooking spray.
Soften the gelatin in a small bowl by combining it with the cold water, stirring with a fork.
Heat the cream in a small pot over low heat until hot but not simmering. Remove it from the heat and whisk in the softened gelatin. Set aside and let cool to room temperature.
In the bowl of a standing mixer, add the cream cheese and beat until smooth. Add the brown sugar, 2 teaspoons of the pumpkin pie spice, salt, and vanilla. Scrape down the sides of the bowl with a rubber spatula. Add the sour cream, maple syrup and pumpkin pie filling. Mix until well blended. Slowly drizzle in the heavy cream and gelatin mixture.
Evenly divide the pumpkin filling among the 2 muffin tins, about 1 1/2 tablespoons per muffin. Once all of the cups are filled put a ginger snap cookie onto the pumpkin filling in each tin. Cover with plastic wrap and refrigerate until set, about 2 hours.
To remove, put some hot water in a sheet tray. Put the muffin tins in the hot water for 30 seconds. Arrange a clean sheet pan on top of the muffin tin and invert. Carefully lift the muffin tray up to release the tarts. Arrange them on a serving platter.
In a chilled bowl add the cream, powdered sugar, and remaining 1/2 teaspoon of the pumpkin pie spice. Beat with a hand mixer until stiff peaks form. Put a teaspoon dollop of whipped cream on top of each tart before serving.