What can I use for the Walnut Coffee Cake if I don't have access to the instant espresso coffee?
Nigella's Coffee And Walnut Layer Cake (from KITCHEN) is made with instant espresso powder. This powder is good for cooking as it is strong in flavour and also has a fine texture, so it can be added easily to cake batters. However for this particular cake it is possible to use a strong liquid form of coffee. If you have instant coffee granules then you can use these, but you need to increase the quantities and dissolve them first in some boiling water.
For the cake sponge you should use 4 1/2 teaspoons of instant coffee and dissolve this in 1 tablespoon of water from a just-boiled kettle, adding an extra drop of water if necessary. Mix up the cake batter without the espresso powder and then add the hot coffee instead of the milk. This should leave the batter with a soft dropping consistency, though you can add add a tablespoon of milk if the batter is still too stiff. Then bake the cake as directed. For the icing use 1 tablespoon (which is 3 teaspoons) of instant coffee granules instead of the espresso powder and dissolve this in the tablespoon of boiling water.