Slowly add the remaining milk and cream mixture, whisking continuously, until smooth.

Gradually add the sugar, whisking continuously, until stiff peaks form.

Return the mixture to the pot and heat over a medium flame, whisking continuously.

Add butter to mixture one tablespoon at a time, whisking continuously, until all is used.

Whisk chunks of cold butter into the sauce one at a time, whisking continuously.

Return the mixture to the pan and bring to a boil, whisking continuously.

Bring the mixture back to the boil and simmer for one minute, whisking continuously, or until smooth.

Slowly add the cold water, whisking continuously, until well combined.

Mix the cocoa with 150ml cold water in a saucepan, then bring to the boil, whisking continuously.

Pour in eggs and cook over very low heat, whisking continuously with small egg whisk.