To make rainbow bark, firstly line a baking tray with parchment paper.
Then break the chocolate into bits. Place the broken chocolate and oil in a medium heatproof bowl and mix together.
Place the bowl over a pot of gently simmering water. Keep stirring until the chocolate is almost melted.
Remove the bowl and keep stirring until the chocolate is completely melted.
Alternatively, microwave the white chocolate in 30-40 seconds intervals, stirring after each round. Two or three rounds should do.
Immediately pour the melted chocolate onto the parchment paper. Using a rubber spatula, spread it out evenly to about 1/4-inch thickness.
Then place gummies and gems on top and gently press into the wet chocolate.
Cover the rest of the white chocolate with sprinkles.
Let the white chocolate firm up completely at room temperature for about 30 minutes.
Then break it up into large pieces or cut with a sharp knife.
Serve Rainbow Candy Bark immediately. Or store in an airtight container in a cool place.