Dilute gelatin in 1 tbsp. water and leave to swell.
Pour milk into a small saucepan, add coffee and bring to a boil, remove from heat. Beat the yolk with sugar with a whisk and introduce into hot milk. Put the resulting mixture on a slow fire, heat, stirring constantly and not boiling. When the mixture begins to thicken, remove it from the heat and dissolve the gelatin in it. Leave to cool.
Pour sour cream into the cooled mixture, mix. Pour coffee panacotta into tins or cups.
Coffee Panacotta is ready, leave in the refrigerator for 5 hours. Serve with grated or melted chocolate.