I couldn't say for sure if this will fit the bill, because I've never had Baskin Robbins' Chocolate Blast, but give it a try, maybe it's close:

CHOCOLATE BLAST VERSION

2 cups milk
1/3 cup granulated sugar
1 cup chocolate ice cream
2 Tbsp. chocolate syrup
2 cups crushed ice or ice cubes
GARNISH:
whipped cream
dash of cocoa powder

Combine milk and sugar in a blender and mix on medium speed for 15 seconds to dissolve. Add ice cream, chocolate syrup, and ice then blend on high speed until smooth and creamy.

Pour drink into two 16-oz. glasses. Add whipped cream to the top of each drink followed by a sprinkle of cocoa powder.

Makes 2 large drinks

Lisa