Step 1: Heat the Milk and Cream

• Pour the milk and cream into a heavy-bottomed saucepan.
• Add the vanilla pod and seeds (or vanilla extract).
• Heat gently over medium heat until just below boiling point, then remove from heat and let it infuse for 5 minutes.

Step 2: Prepare the Egg Mixture

• In a heatproof bowl, whisk the egg yolks, caster sugar, and cornflour (if using) until pale and smooth.

Step 3: Combine and Temper

• Gradually pour the warm milk mixture into the egg mixture, whisking continuously to temper the eggs.
• Strain the mixture back into the saucepan to remove the vanilla pod and any lumps.

Step 4: Cook the Custard

• Heat the custard mixture over low heat, stirring constantly with a wooden spoon or whisk.
• Cook until the custard thickens enough to coat the back of a spoon. Do not let it boil to avoid curdling.

Step 5: Serve or Store

• Once thickened, remove the custard from heat and pour it into a jug for serving.
• If not serving immediately, cover the custard with cling film directly on the surface to prevent a skin from forming.