Remove from heat, add the sweet almond oil and leave to cool (It should cool until only just warm).
Add fragrance as required (the equivalent of a few drops of essential or fragrance oil per fizzin' melt is sufficeint.
Colour can be added a little at a time and stirred/whisked (hand whisk) to achieve enough depth.
Remember, once set solid the background colour of the cocoa butter will be opaque off-white). If you are using ultramarines or oxides to colour, be sure the mixture is fairly cool before adding them, or they will not disperse and colour the mixture.
Whilst the cocoa butter is cooling, mix the citric acid and bicarbonate of soda together in the bowl, ensuring there are no lumps. You can seive it if it helps.
Once the cocoa butter has cooled but is still completely liquid, add the citric acid/bicarbonate of soda mixture.
Stir thoroughly (if it starts fizzing and expanding the cocoa butter is too hot, so try a little first).
Then spoon into ice cube tray moulds and cool immediately in the freezer or ice box.
Don't actually freeze them, just ensure they are very cold and completely solid.
Press out of ice cube moulds as you would an ice cube and leave at room temperature.