Put the eggs and milk in a mixing bowl and beat, using an electric whisk. Beat in the cooled treacle mixture, then sift over the remaining dry ingredients and fold in, along with the lemon zest, until just combined.
Divide the mixture between the prepared tins. Bake for 20-25 minutes, until risen and a skewer inserted in the centre comes out clean. Leave to cool in the tins for 10 minutes, before turning out onto wire racks to cool completely.
For the buttercream, beat the butter and vanilla seeds in a bowl. Gradually add the icing sugar, beating until pale and fluffy; set aside.
Using a serrated knife, cut the sponges in half horizontally to make 4 layers. Sandwich the sponges together with a layer of buttercream, then spread the top with a slightly thicker layer to cover. Thinly spread the remaining buttercream around the sides, scraping of the excess to achieve a ‘naked’ look.
To make a decorative wreath, weave the fresh herbs in a circle and arrange on top of the cake. Rinse the cranberries, then roll in the sugar. Arrange in and around the wreath.
Tip: To make the sponges less crumbly before icing, or even to save time on the day, you can bake them up to 2 days in advance, wait for them to cool and then wrap them in foil and baking paper, before storing them somewhere cool.
See more Adventurous Christmas baking recipes
As part of a healthy balanced diet, we recommend this recipe for a special occasion or treat.