Heat the cream, sugar and espresso until hot in a saucepan.

In a large bowl whisk together the yolks until smooth. Slowly pour in the hot cream mixture (very slowly or eggs will cook and curdle), about 2 Tbsp at a time until everything has been added. Whisk in the espresso powder if desired.

In two ramekin dishes divide up the chocolate, then pour over the cream mixture.

Place into slow cooker and pour in boiling water to half way up the sides of the ramekins.

Cover and cook on high for 1-2 hours or until custard is set around edges but still soft in center. Remove and cool to room temperature.

If not eating right away, place plastic wrap on surface of custards and chill.

Sprinkle a few teaspoons of raw or Demerara sugar on top of custard and place under broiler or torch until melted. Serve immediately.