1. Preheat oven to 325 degrees Fahrenheit (170 degrees Celsius). To prepare dough, place nuts in food processor and process until it becomes a fine powder. Add remaining dough ingredients, except for ground hazelnuts, and mix until it is a soft, smooth dough. Line a 9×13-inch (23×33-cm) pan with Gefen Parchment Paper and grease it with a bit of melted margarine. Press the dough into the pan in an even layer. Bake for 12–15 minutes.
2. Meanwhile, prepare the sugar syrup. Place the sugar and water in a small saucepan and bring to a boil. Cook uncovered for five minutes over a medium flame. Remove the cake layer from the oven and brush the hot syrup over it immediately.
3. To prepare the chocolate cream, place the two types of chocolate in a bowl. Heat the parve whipping cream and pour over the chocolate pieces. Wait one minute. Mix together until melted.
4. Soften margarine in microwave (don’t melt it). Gradually add it to cream and mix until smooth. If the chocolate doesn’t melt completely, place bowl in microwave for a few seconds to finish melting. Mix until the cream is very smooth.
5. Pour chocolate cream onto the cake. Wait about 30 seconds then scatter the ground hazelnuts on top. (If you don’t wait, the hazelnuts will sink into the chocolate and disappear. If you wait too long, the chocolate will harden and the nuts won’t stick.) Let stand until the chocolate becomes firm and then refrigerate for at least two hours.
6. Remove from refrigerator and let stand at room temperature for 15 minutes.
7. Slice into 1¼ x 1¼ inch (3 x 3 cm) squares with a long, sharp, non-serrated knife dipped in boiling water. (Dry with a paper towel between each cut.) Store in a sealed container with parchment paper between each layer. Freeze.