In a small bowl stir together the cream and sour cream. Cover and refrigerate overnight.
Let the sour cream mixture come to room temperature. It should take about 30 minutes. Preheat the oven to 250 degrees C.
In a large bowl mix the sugar, copha and egg yolk together using an electric mixer. Stir the vanilla and bicarb soda into the sour cream mixture. Stir the sour cream mixture into the bowl with the sugar and copha until well blended. Combine the flour and baking powder; stir into the batter until fully incorporated.
Place the dough on a well-floured surface as the dough will be sticky. Use ping pong ball sized pieces of dough and roll out into an 20cm rope. Form into a figure eight and pinch the ends together. Place on ungreased baking trays.
Bake for 5 minutes in the preheated oven or until slightly brown. Cool completely before storing in an airtight container. Store at room temperature for up to 5 days or 1 month in the freezer.