Prepare the bananas. Peel the bananas and slice each one into rounds roughly 1 cm thick. You should get about 7–9 slices per banana. Lay the slices flat on a cutting board and use a small ghost-shaped cookie cutter (about 3–4 cm tall) to press out a ghost from each round. If you do not have a ghost cutter, use a small knife to trim the round into a ghost silhouette—round top, two small indentations for the shoulders, and a straight base. You will feel the banana give gently under the cutter; the edges should be clean, not ragged.

Freeze the banana ghosts. Line a baking tray with greaseproof paper. Arrange the cut banana ghosts in a single layer, making sure they are not touching. Slide the tray into the freezer and leave for 30 minutes. The bananas should feel firm to the touch and look slightly pale on the surface. This step is essential: frozen bananas hold their shape when dipped and help the chocolate set almost instantly.

Melt the white chocolate. Break the white chocolate into even pieces and place it in a heatproof bowl together with the coconut oil (if using). Set the bowl over a saucepan of barely simmering water—make sure the bottom of the bowl does not touch the water. Stir gently with a dry spoon every 30 seconds. The chocolate will look dull at first, then slowly turn glossy and fluid. Once it is completely smooth and runs off the spoon in a thick ribbon, remove the bowl from the heat. Do not let any steam or water droplets get into the bowl, or the chocolate will seize into a grainy mess.

Dip the frozen banana ghosts. Take the tray of frozen banana ghosts out of the freezer. Working with one piece at a time, drop a ghost into the melted white chocolate. Use a fork to gently turn it until every surface is coated. Lift the fork and tap it lightly against the rim of the bowl so the excess chocolate drips off. You will see the chocolate firm up almost immediately against the cold banana. Place the coated ghost back on the greaseproof paper. Repeat with the remaining pieces, but work quickly—once the chocolate in the bowl starts to thicken, re-warm it gently over the saucepan for a few seconds.

Add the faces. While the chocolate coating is still wet, press two dark chocolate chips into each ghost for eyes and one slightly lower down for a mouth. Press them in just far enough so they stay put—if you push too hard, the chocolate shell may crack. The chips should sit flush with the surface, not buried. Work in batches of 4–5 ghosts at a time so the coating does not set before you finish adding the features.

Chill until firm. Return the tray to the refrigerator (not the freezer) and leave for at least 20 minutes. The white chocolate will harden to a snappy shell, and the banana inside will soften back to its original texture as it thaws gently. If you sprinkle desiccated coconut over the top for a snowy look, do it immediately after adding the chocolate chips, while the coating is still tacky.