Combine the water and sugar in a nonreactive medium-size saucepan and place over high heat. Bring to a boil and add the cassis. Stir gently to combine and remove from the heat. Pour the mixture into a 5 x 9-inch loaf pan or a rectangular shallow dish about the same size; it should make a layer about V2 inch thick. Place in the freezer until solid, about 2 hours. (At this stage, the mixture can be stored in the freezer, well wrapped in plastic wrap, for up to three weeks.)
To unmold, dip the pan in hot water for about 5 seconds. Run a sharp paring knife around the edges to loosen the sides of the frozen mixture from the pan. Center a small cutting board over the pan and flip over the board and pan at the same time so the pan is on top. Lift the pan. If the pan does not come off, you will need to dip it in water again. Use a serrated knife to cut the frozen mixture into l/2-inch-wide strips about 3 inches long (or to fit in the glass you are using). Place one cassis stick in each glass and add Champagne. As the cassis sticks melt, they add a delightful fruity flavor to the Champagne.
Variation: If you cant find cassis, use fresh blueberries
Recipes Courtesy of Jacques Torres, Pastry Chef, Le Cirque 2000 and author of "Dessert Circus At Home"