Edy's Frozen Custard Blackberry Sodas: Your entire family will think this frozen treat is berry delicious! Begin with a scoop of our extra thick and creamy Old Fashioned Vanilla Frozen Custard. Then, simply layer Frozen Custard and blackberry syrup (recipe below) into your glass. Top it off with soda water and blackberries! Blackberry syrup: boil down 1 cup fresh blackberries, 1/2 cup sugar, and 3 tablespoons lemon juice; then separate the liquid and the solids to make a syrup and a compote.