The bisque can be made and stored in the fridge for up to 24 hours. It can also be frozen for up to three months.
Put the butter in a saucepan on a medium heat, allow it to melt, and when it is foaming, add the finely chopped shallots and the crushed garlic. Season with salt and freshly ground black pepper and cover with a butter wrapper, if you have one, or some greaseproof paper, and a lid. Turn the heat down to low and cook gently to sweat the shallots. This should take about 7-8 minutes.
While the shallots are cooking, use a rolling pin to crush and bash the prawn heads, claws and shells into smaller pieces. They don't need to be too small, but the more broken up they are, the more flavour you'll extract from them.
Once the shallots have softened, add in the bashed-up pieces of heads, claws and shells, and cook, uncovered (stirring regularly) with the heat turned up for about 6-8 minutes, until you can smell the shells slightly toasting and see them turning light golden in colour.
Add in the tinned chopped tomatoes or the fresh chopped tomatoes, whichever you're using, the light chicken stock or the fish stock, whichever you're using, and the sugar and cook over a high heat for 10-15 minutes until the tomatoes have softened completely. Pour the bisque into a liquidiser or food processor and whizz it up for a few minutes to break up the prawn shells.
Pour the bisque through a sieve into a clean saucepan and place on a medium heat. Add the cream and the brandy, if you are using it, and season to taste with some more salt and freshly ground black pepper. You may need to add a pinch more sugar if you're using tinned tomatoes. When it's hot, sprinkle the bisque with the chopped parsley and serve.