Place about 5cm of water in a small saucepan and bring to the boil. Reduce the heat to a simmer, then place 200g cocoa butter into a heatproof bowl and place it over the water - it shouldn't actually touch the water.
Allow the cocoa butter to melt and then carefully remove from the heat.
Transfer to a jug (this makes it safer for the kids as it's not hot and also makes it easier for them to pour the liquid into the moulds). Carefully add 3 tbsp maple syrup and 1 tsp vanilla extract and whisk in.
Next pour in the 50g cacao powder and whisk that in until smooth.
You will also need a silicone mould. This made enough for three moulds, or around 30 chocolates, so reduce the quantities if you don't want this many or use fairy cake cases for the remainder.