1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius).
2. Grind the graham crackers in a food processor until very fine. Add melted margarine and mix.
3. Pour into an eight-inch square pan (or a nine-inch round pan) and flatten with the back of a measuring cup. Bake for 10 minutes.
4. Beat the eggs in an electric mixer on high until they are creamy yellow. Add sugar very slowly.
5. Meanwhile, melt the chocolate in a microwave for one minute. Remove from microwave and stir until all the chocolate is melted.
6. Add dissolved coffee, oil, cocoa powder, salt, and vanilla to the eggs and mix well. Add the chocolate and mix until just combined.
7. Remove crumbs from oven, pour the chocolate mixture over them, and bake for another 20 minutes. Let cool and cut into 16 squares.
Top each square with a marshmallow toasted over a fire until warm and gooey! Alternatively, arrange marshmallows on the squares and place under the broiler for three minutes or until the marshmallows are brown.