1. Heat oven to 375 degrees F.
2. Drain the syrup from the canned peaches into a small saucepan. Bring the syrup to boiling. Reduce the heat to medium-high; simmer until the syrup is reduced to about 1/2 cup, 10 to 15 minutes. When there are about 3 minutes of simmering time left, stir 2 tablespoons of the peach schnapps into the syrup.
3. Remove the saucepan from the heat. Stir in the drained sliced peaches.
4. Place the biscuits on an ungreased baking sheet. Sprinkle the top of each biscuit with 1/4 teaspoon of the cinnamon-sugar.
5. Bake the biscuits in the 375 degree F oven until they are puffed and golden, about 13 minutes. Remove the baking sheet from the oven. When the biscuits are just cool enough to handle, split each of them in half horizontally.
6. While the biscuits are baking, in a small bowl, with an electric mixer on medium speed, beat together the heavy cream, the remaining 2 tablespoons peach schnapps and the remaining 2 tablespoons cinnamon-sugar until medium peaks form.To assemble the shortcakes:
7. Place the bottom of a biscuit on a dessert plate. Top with 1/3 cup of the peaches in the thickened syrup. Then top with a dollop of whipped cream. Place the biscuit top on the whipped cream. Repeat assembling the remaining shortcakes with the remaining biscuits, peaches and whipped cream. Serve the shortcakes slightly warm. Makes 8 servings.