Boil the sugar and water together to a thick syrup, and remove from the heat before the colour deepens. Melt the butter, stir in the semolina and brown lightly. Add ground almonds and almond and vanilla essence. Add this to the syrup, stirring continuously over a low heat and until it thickens. Cook for a further 2 minutes. Allow to cool, then roll out on a board dusted with icing sugar. Scatter the chopped cherries and walnuts over and roll into a swiss roll shape. Wrap in greaseproof paper and leave in refrigerator overnight. Slice into ½ inch widths.