To a small pot, add milk and heavy cream. Bring it to a simmer on medium heat until small bubbles start coming to the surface.
Turn off heat and add earl grey tea bags. Cover and steep for 10 minutes.
Squeeze out all the liquid in the tea bags by pressing them against the side of the pot with a spatula or pressing them through a small fine mesh sieve. Discard the tea bags. Turn heat back to low and stir in the chopped chocolate until completely melted.
Divide the hot chocolate into mugs and top with toasted marshmallows or whipped cream.