Line two 30cm / 12in by 2.5-cm / 1-in diameter PVC tubes with acetate. Place the tubes on a sheet pan in the freezer.
Churn or pacotize the banana ice cream, pour into a piping bag and pipe into the prepared tubes. Smooth out the top of the tubes with an offset spatula. Place in the freezer to harden.
Once hardened, remove the frozen banana ice cream from the tubes and reserve frozen with the acetate on.
Line two 30cm / 12in by 6.25cm / 2.5in diameter PVC tubes with acetate. Place the tubes on a sheet pan lined with a nonstick rubber mat in a standing position in the freezer.
Churn or pacotize the caramel ice cream, pour into a piping bag and pipe into the prepared tubes three-quarters up. Take the acetate off the hardened banana ice cream inserts and insert into the soft caramel ice cream. Make sure that the insert is centered. Smooth out the top of the PVC tube with an offset spatula. Freeze to harden in a standing position and reserve until needed.
Place the banana bread rectangles on a 30cm / 12in long by 5-cm- / 2-in-wide Plexiglas.
Soak each cake with 100g / 3.53oz elderflower syrup.
Reserve refrigerated until needed.
Place a half sheet pan lined with parchment paper in a freezer.
Cut the frozen caramel ice cream and banana tube in four 2-in-wide pieces. Cut one 4-in-piece. Cut the 4-in-piece on the diagonal. Cut one of the 2-in pieces in half. Leave the acetate on the ice cream while cutting it. Re-freeze the cut pieces with the acetate still on.
Prepare a spraying area and bring the white chocolate spray to 37°C / 100°F.
Fill a compressor with the melted white chocolate spray.
Take the acetate off the cut pieces of ice cream and spray to coat completely.
Return to the freezer for 10 minutes.
Place the sprayed pieces of ice cream on the banana bread in a line. Return to the freezer.
Fill a cornet with melted dark chocolate. Pipe the desired design on the cake.
Reserve frozen in an airtight container until needed.