Line a tray-bake or straight sided roasting tin 30 cm x 23 cm (12" x 9") with baking parchment.
Place all the ingredients in a large mixing bowl, I used my stand mixer but you can mix it with a wooden spoon or an electric hand mixer, until it is thoroughly mixed.
Put all of the mixture into the tin and spread evenly.
Bake for 25-30 minutes until the cake has risen and is evenly brown.
Leave to cool in the tin.
Once the cake is cool, sprinkle your work surface and rolling pin with icing sugar and roll out 350g of the marzipan into a rectangle the size of the cake.
Put a tbsp of apricot jam, jelly or honey into a pan with a little water, heat until the jam has melted. Brush the jam mixture all over the cake.
Place the marzipan on the cake, pressing down gently to stick it to the cake.
Use the remaining marzipan to make 18 balls and use a little more jam to stick them in place with one ball for each portion of the cake.
Optional
If liked, you may wish to brush the top of the marzipan and the decorations with more jam/jelly/honey then place under the grill or use a chef's blow torch to brown the top of the marzipan.
Leave to cool and cut into 24 squares.
Notes
Slice, pack in containers, and freeze for up to 3 months.