Combine crust ingredients in a bowl and mix well. Add a tablespoon of water if the mixture does not stick together when you pinch a bit between your fingers.
Spread crust mixture into a 9″ springform pan evenly across the bottom and 3/4″ up the sides. It helps to use a flat-bottom glass or measuring cup to press it out.
Bake at 350º 12 minutes. Remove and set aside.
For the filling, combine the cream, cardamom, and coffee in a small pot. Heat over medium, stirring constantly, until cream begins to steam and small bubbles appear around the edges.
Remove from heat and stir in the broken chocolate. Stir until melted.
Stir in the butter and stir until melted.
Pour immediately into crust.
To make the spiderweb: Break the chocolate into chunks and put in a small pitcher or something else with a spout, add the cream and microwave about 20 seconds. Stir until melted. Pour onto the still-warm tart in a spiral. Drag a skewer from the center of the tart out to the edges in a spoke pattern to make the web. See video for demonstration.