Method

1. Heat both soy milks in a small, heavy-based saucepan over medium heat until simmering. This should take about 5 mins. You can tell it is at a simmer when small bubbles start to appear around the edges. Do not let it boil. Take it off the heat.
2. Whisk together the egg yolks and 50g of the caster sugar in a large mixing bowl, using a wire whisk or hand blender, until thick and pale. Pour the soy milk mixture into the egg mixture and quickly whisk until well combined.
3. Wash the saucepan then add the remaining 200g caster sugar and 2 tablespoons of water and place over low heat. Stir until sugar is dissolved then increase the heat to medium and boil, not stirring, until it turns a rich golden colour. This will take about 5 minutes. Add the vanilla bean and scraped seeds and take it off the heat.
4. Slowly pour the soy milk mixture into the caramel – carefully, as it will splatter – and whisk well. Place back onto the heat and stir until any lumps melt, stirring constantly, until thickened to form a custard. This will take about 3 minutes. You can check if it is thick enough by dipping the spoon into the custard and then running your finger along the back of the spoon. If the fingermark remains in place, it is ready.
5. Cool in the saucepan until there is no steam rising from the custard, then transfer to a heatproof container. Cover the surface of the custard with plastic wrap to prevent a skin forming and chill in the fridge for at least 4 hours or until completely cold.
6. Pour the cold custard into the bowl of an ice cream maker, set to desired setting and churn. When machine specifies you can add mix-ins, sprinkle in the chopped popcorn and resume churning. Once mixture is frozen transfer to a freezer-safe container and freeze for up to one week.

Notes: I used the Breville Smart Scoop ice cream maker to create this recipe. I pre-cooled the machine for 15 minutes before churning and set it to the first setting in the ice cream section.