Preheat the oven to 180C
Heat milk, cream and shell of vanilla bean in a pan over low heat until slight bubbles form on the edges. Take off heat.
Place the eggs, scraped vanilla and sugar in bowl of stand mixer. Whisk on speed 2 for 2 minutes until sugar is almost dissolved.
Reduce speed to lowest, put the splatter screen, and gently pour in the vanilla infused milk, whisking continuously for 30 seconds.
Strain the custard into a jug/saucepan, and then pour into the prepared ramekins.
Place ramekins in a 9′ X 9″ square pan. Gently pour in water into the tray to come up half around the ramekins.
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Bake for about 45 minutes until the custard begins to set, a bit wobbly in the middle.
Allow to cool, then chill covered for a few hours, preferably overnight.
To serve, run a butter knife gently around the tip to loosen it, place a platter over the ramekin, turn over swiftly, and then shake to release. Top with toasted walnuts if desired.