Puree the raspberries in a food processor and put them in a pan with the butter
and sugar. Heat gently, stirring constantly, until the ingredients are melted and
Let them cool to tepid, then stir in the eggs.
Set the pan back on the heat and continue to cook over very low heat, stirring
all the time, until the curd thickens enough to coat the back of the spoon, 20 to
25 minutes. Don't let the curd cook too fast or get too hot as it will curdle.
Work the curd through a sieve to remove the seeds.