1. Preheat oven to 350 degrees F. Line an 8-inch square baking dish with foil. To prepare the crust: 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.
2. Meanwhile, to prepare the filling: Put the chocolate in a medium microwave-safe bowl; heat at 75-percent power until softened, about 2 minutes. Stir, and continue to microwave 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.
3. 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 melted chocolate into the wet ingredients and mix until smooth.
4. 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, about 25 to 30 minutes. Cool on a rack.
5. To prepare the glaze: Put the chocolate, butter, and corn syrup in microwave-safe bowl. Heat the glaze in the microwave at 75-percent power until melted, about 2 minutes. Stir the ingredients together until smooth and add the sour cream. Spread the glaze evenly over the warm cake. Cool completely, then refrigerate overnight. Cut into small bars or squares. Serve chilled or room temperature.
Store the bars, covered, in the refrigerator for up to 5 days.
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