In a small saucepan, over low heat, melt the butter. Stir in the molasses and the vanilla, then remove from the heat, pour into a large bowl and cool to room temperature.

Sift the flour, baking soda, spices and 1 cup of the sugar in a medium bowl. Stir in the chopped crystallized ginger.

Lightly beat the egg in a small bowl and add to the cooled butter-molasses mixture. Fold the flour into the molasses mixture and combine well. Wrap the dough in plastic wrap and chill for 20 to 25 minutes.

Preheat the oven to 375 degrees F.

Put the remaining 1/4 cup of sugar in a shallow bowl and set aside. Take 2 tablespoons of the dough and roll it into a ball, then into the sugar. Repeat with the rest of the dough. Bake until flat and just starting to dry out on the edges, about 10 to 14 minutes. Bake in batches of 8 on a baking sheet lined with a silicone baking mat or aluminum foil. Remove to a cooling rack. This can be done ahead, cooled and stored tightly covered.

Cut the packaging from the ice cream pints and cut the ice cream into 1-inch thick rounds. Put 1 cookie face down on a 8-inch square of waxed paper and top with the ice cream, matching the diameter of the cookie as close as you can, trim if needed. Top with another cookie, face up and wrap the waxed paper around the stack, and then wrap tightly with a piece of plastic wrap. Repeat, placing the finished stackers into the freezer as they are completed. Let them freeze for 30 minutes and remove wrapping to serve.