Start with chopping 4 oz of bittersweet chocolate into small chunks. These melt evenly in the hot chocolate.
If you are using chocolate chips, I would recommend melting them in the microwave and then adding them to the hot chocolate.
Sift cocoa powder, and cornstarch in a saucepan. Then add castor sugar, bittersweet chocolate chunks, and chai spice.
Now add milk to the saucepan while whisking so no lumps are formed.
Simmer the hot chocolate on medium-low flame and let it simmer. It should start to thicken.
You want to make sure not to boil the hot chocolate. Once you see the hot chocolate simmering, take it off the flame.
You can add vanilla now if you wish too.
Ladle the hot chocolate into the mugs and serve it hot.
Top it with marshmallows, and use a blow torch to give it a smoky s'mores effect!
You can also top with with vanilla flavored whipping cream and chocolate shavings to keep it simple!