Preparation Whip cream, 2 tablespoons sugar and 1/2 teaspoon vanilla in medium bowl until peaks form. Fold in 1/4 cup chocolate chips. Cover; chill up to 4 hours. Combine remaining 1/4 cup sugar and 3/4 cup chocolate chips in heavy medium saucepan; add milk and cocoa. Whisk over medium heat until mixture almost simmers and chocolate melts. Whisk in remaining 1/2 teaspoon vanilla. Ladle hot chocolate into mugs. Whisk chocolate-chip cream to thicken if deflated; dollop cream atop hot chocolate.
Preparation Whip cream, 2 tablespoons sugar and 1/2 teaspoon vanilla in medium bowl until peaks form. Fold in 1/4 cup chocolate chips. Cover; chill up to 4 hours. Combine remaining 1/4 cup sugar and 3/4 cup chocolate chips in heavy medium saucepan; add milk and cocoa. Whisk over medium heat until mixture almost simmers and chocolate melts. Whisk in remaining 1/2 teaspoon vanilla. Ladle hot chocolate into mugs. Whisk chocolate-chip cream to thicken if deflated; dollop cream atop hot chocolate.