As garnish, if desired. -- Put the raisins and grated lemon rind into a bowl with the whiskey, and leave overnight to soak. Grease a 7-inch cake pan, and line the bottom with parchment; preheat oven to 350F. Cream the butter and sugar until light and fluffy. Separate the eggs and sift the flour, salt, cloves and baking powder into a bowl. Beat the yolks into the butter and sugar one by one, including a spoonful of flour and beating well after each addition. Gradually add the whiskey and raisin mixture, alternating with the remaining flour. Do not overbeat at this stage.
Finally, whisk the egg whites until stiff and fold them into the mixture with a metal spoon. Turn into the prepared pan and bake in the preheated oven for about 1 1/2 hours, or until well risen and springy to the touch ~- or test with a skewer: when it comes out clean, the cake's ready.
Turn out and cool on a wire rack.
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Meanwhile, make the icing by mixing the lemon juice with the sieved confectioners' sugar and just enough water to make a pouring consistency.
Put a dinner plate under the cake rack to catch the drips, and pour the icing over the cake a tablespoonful at a time, letting it dribble naturally down the sides. Don't worry if a lot of it ends up on the plate underneath -- just scoop it up and put it on top again. When the icing has set, it can be decorated with crystallized lemon slices if you like.
