Preheat the oven to 190C or 170C if using a fan oven. Grease and line the base of four 20cm sandwich tins with a disc of parchment paper.
Beat the soft butter and sugar together until pale and creamy. Slowly add the honey, and continue to beat until well combined. Add the eggs one by one, ensuring each egg is fully incorporated before adding the next.
Add the flour, baking powder, lavender and orange zest, and mix until just combined.
Divide the sponge mix into the four prepared tins, and bake in the preheated oven for 15-20 minutes, until lightly golden and a skewer inserted into the centre comes out clean.
Leave the sponges to cool for a few minutes in the tins before turning out onto a wire rack to cool completely.
For the Frosting:
Beat the softened butter in a bowl until pale and soft. Slowly add the icing sugar, and continue to mix until smooth and creamy, for about 2-3 minutes.
Add the vanilla. Set the frosting aside until ready to assemble.
Presentation and Assembly:
Trim the tops of the sponges so that they are all even. Place the first sponge on a cake stand or turntable and pipe or spread some of the frosting on top. Continue with the remaining sponges.
Use the frosting to ice the top and sides of the cake, and finish with lavender and orange slices to serve.