Gently warm the cream in a heavy based pan, until bubbles appear at the edge; do not allow it to boil. Remove from the heat and infuse with the torn basil leaves and stalks. For best results place in the refrigerator and leave overnight.
To continue making the brulee, gently reheat the cream again, until bubbles appear around the edge.
Meanwhile, beat the egg yolks with the caster sugar in a large heatproof bowl until creamy.
Pour the cream through a sieve onto the egg yolks, stirring all the time. Stir in the blended cornflour, then place the bowl over a saucepan of boiling water and heat gently, stirring continuously until the custard thickens (this will take approximately 8-10 minutes).
Divide the custard into 4 small ramekin dishes or a large shallow heatproof dish.
Sprinkle the raspberries over, letting them find their own level. Leave to cool, then refrigerate until required.
Preheat the grill to a high heat.
Sprinkle the demerara sugar over the brulees, making sure the edges are covered and grill until the sugar bubbles and caramelises.