First, start by turning on your Instant Pot and setting it to the saute function.
Next, add in the milk, heavy cream and evaporated milk. Stir to combine.
Add in the semi-sweet chocolate chips, unsweetened cocoa powder and white granulated sugar. Stir for about 1 minute to melt the chocolate chips. Use a whisk to break up any lumps from the cocoa powder.
Next, add in the vanilla extract and cinnamon stick. Cancel the saute function and close the lid.
Cook on high pressure for 2 minutes.
Wait for it to natural release which should take about 10 minutes. Do not hit the quick release button because the hot chocolate will likely come spewing out.
Open the lid once the pin (valve) has dropped which means the pressure has been released.
Finally, give it another stir and serve it with marshmallows or toppings of your choice! Use the keep warm function until all of the hot chocolate in the instant pot is finished.