Ingredients

• 4 cups granulated sugar
• 1/2 vanilla bean, split crosswise (see tips, below)
• 1 1/2 pounds high-quality semisweet chocolate, coarsely chopped
• 8 ounces milk chocolate, coarsely chopped
• 2 cups unsweetened cocoa powder, preferably Dutch process (see tips, below)

Instructions

1. Place sugar in large bowl. Split half vanilla bean lengthwise, scrape seeds into sugar, and add pod. Work seeds in with your fingers. Cover snugly with plastic wrap and let stand overnight at room temperature.
2. In food processor fitted with metal blade, process semisweet chocolate and milk chocolate until finely ground, using 4-second pulses. (Process in two batches if necessary.)
3. Remove pod from sugar. Add ground chocolate and cocoa powder to sugar and whisk to blend.
4. Store mix airtight at room temperature for up to six months.
5. For each serving, heat 8 ounces milk in small saucepan over medium heat until scalded (or microwave 2 1/2 minutes at full power). Whisk in 1/4 to 1/3 cup mix. Serve with unsweetened softly whipped cream or marshmallows.