Place the raspberries and lemon juice in a pan over a low heat. Cook until the raspberries break down and become juicy.
350 g (12 oz) raspberries (fresh or frozen), 60 g (¼ cup) lemon juice
Press the raspberry mixture through a fine mesh sieve into a bowl or jug to remove the seeds. Really scrape it through using the back of a spoon or a spatula to extract as much of the pulp as possible, you should have about 300g of puree after straining it. Discard the seeds.
Place the cornflour in a saucepan and gradually whisk in the milk making sure that there are no lumps. Whisk in the sugar.
30 g (3 packed Tablespoons) cornflour (cornstarch)*, 80 g (⅓ cup) unsweetened non-dairy milk (I use soy), 115 g (½ cup + 1 Tablespoon) caster or granulated sugar
Whisk in the raspberry puree then place the pan over a medium-low heat. Stir constantly until the curd comes up to a boil and thickens.
Remove the pan from the heat and add the butter. Whisk until melted and smooth. It will look split at first but keep whisking and it will come together.
70 g (5 Tablespoons) vegan block butter
Transfer the curd to a heatproof container and cover with baking paper or clingfilm directly on the surface to prevent a skin from forming. Refrigerate for at least a couple of hours, until cooled and thickened.
The curd will set quite firm in the fridge; when you are ready to use it, give it a really good stir and it will become smooth and creamy again.