1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius). Trace a circle of Gefen Easy Baking Parchment Paper to match the bottom disc of a nine-inch (23-centimeter) springform pan. Cut it out and place on bottom of pan. Spray with baking spray.
2. Place melted butter or margarine in a large bowl. Add remaining ingredients and mix until well incorporated. Pour into prepared springform pan. Bake for 20 minutes. Allow to cool completely.
3. In the bowl of a stand mixer fitted with the beater attachment, whip the parve whipping cream, adding egg yolks and confectioners’ sugar as it beats. Add vanilla sugar, soy milk, and raw tahini and mix to combine.
4. With a sharp knife, shave the halva into thin pieces and fold into the ice cream mixture. Pour onto the cooled brownie layer, smooth out, cover, and freeze until set, about eight hours.
5. In a double boiler, melt the ingredients for the chocolate layer. Stir until smooth. Remove from heat, let sit for five minutes, and then pour evenly over the ice cream. It should harden quickly. Cover cake and return to freezer.
6. When ready to serve, run a sharp knife around the edges of the pan to release the cake from the sides of the pan. Open the pan from the bottom and pull up the parchment paper to transfer the cake to a serving dish.