01 - In a small saucepan over medium heat, combine milk and heavy cream. Heat until steaming but do not boil.
02 - Add cocoa powder, chopped dark chocolate, and sugar to the warm liquid. Whisk continuously until chocolate is fully melted and the mixture is smooth.
03 - Stir in mixed berries and simmer for 2 to 3 minutes, gently mashing the berries to release their flavor.
04 - Optionally strain through a fine mesh sieve into heatproof mugs or a pitcher to remove berry solids.
05 - Top each serving with mini marshmallows.
06 - Using a kitchen torch or broiler, carefully toast marshmallows until golden brown, watching closely to prevent burning.
07 - Optionally sprinkle with chocolate shavings and serve immediately.