In 9" microwavable quiche dish, round baking dish or deep pie plate, melt butter on high for 1 to 1 1/2 minutes. Stir in crumbs and 2 Tbsp sugar till evenly coated with butter. Press onto bottom and sides of pan. Microwave at High for 2-3 minutes or till firm. Rotate dish if necessary. In small dish, melt chocolate at Medium (50%) for 2-3 minutes, stirring to help chocolate melt. Set aside. In large bowl, beat cream cheese and sugar till light. Beat in eggs, one at a time, then add sour cream and vanilla and beat till smooth. Pour into baked crust. Drizzle chocolate over mixture in attractive pattern. Microwave, uncovered at Medium (50%) for 14 to 18 minutes, or till cheesecake is almost set in the centre. Rotate dish during cooking, if necessary. Cool on countertop to room temperature, then refrigerate till serving.