Preheat oven to 170 C / Gas 3. Grease and flour a 26cm round tube cake tin.
In a large bowl, cream butter and sugar together with an electric mixer until well mixed. Add eggs, one at a time and beat until mixture is light and fluffy. Blend in flour and salt. Mix in almond extract. Pour batter into prepared tin.
Bake for 60 minutes or until a skewer comes out clean when inserted in the centre of the cake. Cool in tin for 10 minutes. Remove from tin and transfer to a wire rack to cool fully.
Break off tablespoon-sized pieces of the marzipan and shape into holly leaves. Using the tip of a knife, score the shaped holly leaf to resemble veins in the leaves. Mix green food colouring with a small amount of water and brush the holly leaves, repeating until desired colour is reached. Set aside on greaseproof paper.
Break off 2 tablespoons of marzipan and knead in several drops of red food colouring. When colour is bright red, break off smaller pieces. Roll into balls to resemble holly berries. Place on greaseproof paper.
In a small bowl, combine 120g icing sugar and milk. Mix until smooth. When the cake has cooled, drizzle with the glaze and top with almonds. Garnish with the marzipan holly leaves and berries.