01 - In a medium saucepan over medium heat, combine whole milk, heavy cream, and vanilla extract. Warm until mixture is steaming but not boiling.
02 - Whisk in chopped dark chocolate, Dutch-processed cocoa powder, granulated sugar, instant espresso powder, and a pinch of sea salt. Continually whisk until the chocolate is fully melted and the liquid is smooth and velvety.
03 - Reduce heat to low and allow the mixture to simmer for 2 to 3 minutes, stirring frequently to prevent scorching.
04 - Taste and, if preferred, adjust the level of sweetness by stirring in more sugar.
05 - Pour the hot chocolate into heatproof mugs. Top each serving with whipped cream and sprinkle with dark chocolate shavings if desired. Serve immediately.