Melt chocolate and butter first, then add condensed milk — not before. Use 20-second microwave intervals; stir between each. Chocolate scorches fast — short bursts only. Add toppings while warm so they stick. Chill 45-60 min in refrigerator — don't freeze to speed it up. For milk chocolate: reduce condensed milk to 2½ tsp. Keeps covered in refrigerator up to 5 days. Freezes up to 2 months.