Combine crumbs and melted butter; press firmly into the bottom of an 20 cm springform pan. Chill. Combine cream cheese and sugar in a medium bowl. Beat at medium speed of an electric mixer until mixture is smooth and well blended. Add eggs, one at a time, beating after each addition. Add 1- half teaspoons vanilla. Stir in melted chocolate and yogurt, blending well. Pour batter into prepared pan. Place a 13-x 9-x 5 cm baking pan on lower rack of oven. Pour water into pan to a depth of 3 cm. Place cheesecake on middle rack of oven. Bake at 150ºC or 1 hour and 20 minutes or until cheesecake is set. Turn oven off, and partially open oven door; let cake cool in oven. Combine chocolate, 2 tablespoons butter, corn syrup and half teaspoon vanilla in a saucepan. Cook over medium heat until melted; cool slightly. Spoon glaze over cheesecake; chill at least 8 hours. SOURCE: Unbearably Good! Junior Service League of Americus, Georgia America's Best Recipes; A 1988 Hometown Collection; Oxmoor House.