Preheat the oven to 350 degrees F. Spray a 9-inch square baking pan with nonstick spray, and line with a sheet of parchment paper, allowing the excess paper to drape over the sides of the pan.
Place the gingersnap cookies in the bowl of a food processor, and chop finely. Stir in the melted butter, and firmly press the mixture into the bottom of the prepared pan.
Add the cream cheese to the bowl of a stand mixer, mixing on medium-low speed until creamy. Add the sugar and salt mix to combine. Add the eggs and yolks, one at a time, stopping to scrape the bottom and sides of the bowl with a silicone spatula after each addition. Stir in the melted chocolate, spices, lemon zest, molasses, and vanilla. Transfer the batter to the prepared pan.
Place it in a larger baking dish, and pour very hot water into the larger dish until it comes up about 1 inch around the cheesecake pan.
Carefully transfer to the oven and bake for 20 minutes at 350 degrees F. Then, lower the oven temperature to 250 degrees F and bake for another 65 minutes, or until set around the edges but still slightly jiggly in the center. Turn off the oven, and prop the door ajar. Allow the cheesecake to cool slowly in the oven for at least an hour. Refrigerate 2 hours to overnight before removing from the pan and cutting into bars
Garnish cheesecake bars with mini gingerbread cookies or sprinkles!