Preheat oven to 180°C.
Beat the butter, sugar and coffee together until smooth.
Add the eggs and beat well, then add the sour cream and essence and beat.
Add the flour, salt, bicarbonate of soda, baking powder and chocolate to the butter mixture and mix until the dry ingredients are just mixed in.
Spoon equal amounts of batter into a greased muffin pan and bake for 20 minutes or until golden brown in colour.
Allow muffins to cool in pan before turning out onto a wire rack.
Serve plain or with butter, maas or cream cheese