• Pre-heat oven to 180°C / 160°C fan / gas mark 4 and line and grease three 20cm sandwich tins.
• In a large mixing bowl beat the sugars, eggs, buttermilk and olive oil.
• Mash the bananas well then add them to the mixing bowl along with the vanilla.
• Whisk together the cassava flour and ground almonds in a large bowl with the baking powder, bicarbonate of soda, cinnamon, nutmeg and salt.
• Add the dry flour mix into the mixed wet ingredients and beat together until just incorporated.
• Pour evenly into the three sandwich tins and bake in the oven for 20 minutes until golden and an inserted toothpick comes out clean.
• Turn each cake out of the tin onto a cooling rack and leave to cool to room temperature.

Sticky Toffee Ermine Buttercream

Toffee Sauce

• Pour the caster sugar into a medium sized saucepan into an even layer and heat on a gentle temperature as the sugar begins to melt.
• Avoid moving the sugar around too much but you can encourage an even melting by gently shaking the actual saucepan around occasionally if you need to. Keep a careful eye on the sugar and do not leave at all.
• As the sugar has melted it will turn a dark golden tan colour. Watch to make sure it doesn’t get too browned as this means it’s burning.
• As soon as the sugar has melted and has turned that dark golden tan colour then pour in the double cream and the butter. It will rise dramatically up the saucepan so stand back at first for safety.
• Stir the cream and butter into the melted sugar and it will form a thick silky toffee sauce.
• Remove from the heat and pour the toffee sauce into a bowl and chill thoroughly before using.

Roux

• Whisk the cassava flour and 100ml of the milk in a medium sized saucepan (no heat) until smooth.
• Turn the heat on low and whisk continually until the mixture has thickened.
• Gradually add the rest of the milk in a slow stream, whisking hard continuously to avoid any lumps which are quick to form.
• As soon as the mixture reaches a boil and has thickened then remove from the heat immediately and continue whisking for a couple of minutes to remove all the lumps. Strain then leave to cool completely.

Buttercream

• Mix the butter with the icing sugar in a large bowl with an electric beater or stand mixer. Cream for about 5 minutes until very light, pale and fluffy. Scrape the sides of the bowl down every so often to ensure even mixing.
• Add ¾ of the cooled toffee sauce, the cooled roux and salt then mix again on a low speed until smooth and just combined.

Assembly

• Place one of the cake sponges onto a cake board.
• Transfer the buttercream to a piping bag fitted with a 1A piping tip. Pipe ¼ of the buttercream around the surface of the cake sponge in concentric circles to create an even layer of buttercream. Use a palette knife to smooth it.
• Place the second cake sponge on top of the buttercream. Pipe around ¼ of the buttercream and smooth as before.
• Place the final cake sponge on top of the buttercream. Pipe around ¼ of the buttercream and smooth as before.
• Drip the rest of the toffee sauce down the edges of the cake, warming the toffee sauce slightly if it’s a bit solid.
• Decorate the top of the cake by piping simple buttercream drops across the surface using the last ¼ of the buttercream.
• Finally scatter chopped banana chips over the top.