Mix together cocoa, sugar, and salt in a medium saucepan. Whisk in boiling water. Bring this mixture to a bubble. Add milk, stirring constantly, until it is hot being careful not to bring to a boil. Remove from heat and stir in vanilla. If the hot chocolate is too hot for children, add a few splashes of cold milk to cool it down. Pour into cups.
Whip cream until it forms soft peaks with an electric mixer. Add powdered sugar and vanilla until it forms stiff peaks. Fold in crushed candy canes. Serve with hot cocoa.