Step by step

1. Pour the milk into a heavy bottom pan and add the vanilla seeds and the vanilla paste. Bring to a soft simmer.

2. In the bowl of a stand mixer fitted with the Mixer Whisk add the sugar, cornstarch and egg yolks. Mix on speed 6 until a light and fluffy mixture forms.

3. Lower the speed of the stand mixer to 2 and gently stream in half of the heated milk. Mix until the 2 components have combined completely. This step is 'called tempering the eggs'.

4. Return the tempered eggs to the remaining hot milk in the pan and whisk vigoursly until a thick custard forms. This will take about 10 minutes. Sieve the hot custard to remove any lumps.

5. Whisk in the cold butter, cover the bowl with cling film and let chill in the fridge for at least 12 hours. Use the chilled pastry cream to fill sweet pastries.