Source: Every Food (Martha Stewart)
http://www.pbs.org/everydayfood/recipes/steamy_hotchocolate.html
adapted by http://theresalwaysthyme.blogspot.com
1/4 cup unsweetened cocoa powder
1 quart (4 cups) milk
1 cup (6 ounces) semisweet chocolate chips
1 tablespoon vanilla extract
pinch of salt
whipped cream, for serving (optional)
Place cocoa powder in a medium saucepan. Stir in milk, a bit at a time until cocoa mixes in with the milk and isn't clumping; add remainder. Stir. Add chocolate chips; melt over medium heat, stirring occasionally.
Bring to a boil, stirring occasionally. Remove from heat; stir in vanilla and salt. Ladle into mugs with whipped cream, if desired.