To set off the sweetness there's an interesting additional ingredient: a touch of coffee in the crust. For best results, like other cheesecakes, these squares should be chilled overnight so they set completely and slice cleanly.
For the crust: Preheat oven to 350 degrees F. Line an 8-inch square baking dish with foil.
Process the chocolate wafers in a food processor with the butter, sugar, coffee, and salt until fine. Evenly press the crust into the prepared dish covering the bottom completely. Bake until the crust sets, about 15 minutes.
For the filling: Meanwhile, heat the chocolate in a medium microwave-safe bowl; at 75% power until softened, about 2 minutes. Stir, and continue to heat until completely melted, up to 2 minutes more. (Alternatively; put the chocolate in a heatproof bowl. Bring a saucepan filled with an inch or so of water to a very slow simmer; set the bowl over, but not touching, the water, and stir occasionally until melted and smooth).
Blend the cream cheese, sugar, and sour cream together in the food processor until smooth. Scrape down the sides, as needed. Add the eggs and pulse until just incorporated. With the food processor running, pour the chocolate into the wet ingredients and mix until smooth.
Pour the filling evenly over the crust. Bake until the filling puffs slightly around the edges, but is still a bit wobbly in the center, 25 to 30 minutes. Cool on a rack.
For the glaze: Put the chocolate, butter and corn syrup in a microwave safe bowl and heat at 75% until melted, about 2 minutes. Stir the ingredients together until smooth; add the sour cream. Spread the glaze evenly over the warm cake and scatter the crushed candy canes over top. Cool completely, and then refrigerate overnight.
Cut into small bars or squares. Serve chilled or at room temperature.
Store the bar covered in the refrigerator for up to 5 days.
*To crush the candy canes, remove wrappers and place in a resealable plastic bag. Use a rolling pin to roll over and break up the candy into small pieces, about 1/4 inch or so.