01 - Combine whole milk and heavy cream in a medium saucepan and heat over medium heat until steaming without boiling.
02 - Add chopped dark chocolate and chocolate hazelnut spread to the saucepan, whisking continuously until fully melted and smooth.
03 - Taste the mixture and stir in granulated sugar if desired, whisking until dissolved.
04 - Continue heating and stirring frequently for 2 to 3 minutes until the hot chocolate achieves a rich and creamy texture.
05 - Pour the hot chocolate into mugs and garnish with whipped cream, chopped hazelnuts, and chocolate shavings as preferred. Serve immediately.