Cut your marzipan (215g) into cubes and put it into a bowl. Add the water (4 tsp) and knead the marzipan into the water until most of the water has been absorbed into the marzipan (the idea here is to soften the marzipan so it's easier to beat into the buttercream).

Cut your butter (215g) into cubes and beat with an electric mixer on a slow speed until soft.

Add the icing sugar (320g) and beat it into the butter until fully combined. I find it best to add it a little at a time to stop it flying all over the kitchen.

Once the butter and sugar are combined, add the softened marzipan and almond extract (a few drops) and again beat until fully combined.

If you find you have some small lumps of marzipan then you'll need to give the buttercream a quick blitz with a hand blender. Put a few spoonfuls into a bowl, blend until smooth and then repeat until all of the buttercream has been blended.

Check the consistency of your buttercream. If it's a little to thick to be piped then add a little milk (no more than a tsp at a time) and mix to combine. Keep adding a little more until the consistency it right.

Your buttercream is now ready to use.