Once the raspberries are thawed (you can zap them in the microwave for 2 minutes or just heat them in a saucepan if you want to speed it up), place them into a food processor and process on high for 30-60 seconds until you have a puree.

In a heavy based, medium saucepan, over medium heat, heat 1 cup (250ml) of the milk and all the sugar, stirring to dissolve until it starts steaming heavily.

While gently whisking, very slowly drizzle the hot milk into the egg mixture. Don’t pour it too quickly or you’ll cook the eggs.

Return the custard mixture to the pan and cook over medium heat, gently stirring with a whisk the entire time until it starts to thicken and bubble.

As soon as you see the first bubbles appear, continue cooking and stirring for a full minute to activate the starch (in the cornflour).

Remove from the heat and stir in the butter and salt until the butter has melted and is fully incorporated.

Pour the pastry cream into a clean dish and place plastic wrap over the top, pressed to the surface.

Chill to cool completely. You will need to give it a whisk before you use it.

Pastry cream will last for 3-4 days in the refrigerator. NOT suitable for freezing as the mixture can split on thawing.