1Heat oven to 350°F (325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups. Make cake batter as directed on box. Divide batter evenly among muffin cups (about two-thirds full). Press 1 milk chocolate drop in center of each muffin cup.
2Bake and cool as directed on box for 24 cupcakes.
3In medium bowl, beat powdered sugar, butter, melted baking bar and vanilla with electric mixer on low speed until blended. Gradually beat in milk until smooth and creamy. Frost cupcakes; pipe year with melted dark chocolate onto each cupcake. Store loosely covered.