Make the butter ganache

• Melt the white chocolate gently in a bowl over a saucepan of simmering water.
• Warm the cream and pour it over the melted chocolate, stirring until smooth.
• Let the ganache cool to about 35 °C, then blend in the softened butter until glossy.

Prepare the Frost Form

• Assemble the 8, 6 and 4 inch Frost Form rings and place them on a lined tray.
• Pour the butter ganache into each form, filling to the marked line.
• Tap the forms to release air bubbles.

Set the ganache

• Chill the filled forms until the ganache is fully firm.
• Keep them cold until the cake layers are ready to insert.

Insert the cake layers

• Push a cooled sponge layer into each chilled ganache-filled form, pressing down evenly.
• Trim any sponge that rises above the ganache line.

Release and stack the tiers

• Run a warm knife or your hands around the form to release each tier.
• Lift off the forms and smooth the ganache surfaces.
• Stack the 8, 6 and 4 inch tiers on a cake stand, centring each one.

Finish and serve

• Tint any remaining ganache with gel colouring and pipe or spread decorations if desired.
• Chill the assembled cake until ready to slice.