Grease the base and sides of a 1.4L loaf pan and line with plastic wrap, allowing the sides to overhang.
Use a balloon whisk to whisk yolks and honey in a heatproof bowl until thick and pale. Place coconut milk and vanilla seeds in a large heatproof bowl set over a saucepan of just simmering water (don’t let the bowl touch the water). Cook, stirring, for 8 minutes or until hot (don’t boil). Slowly whisk hot coconut mixture into egg mixture until combined.
Return mixture to a heatproof bowl set over a saucepan of simmering water (don’t let the bowl touch the water). Cook, stirring, for 3-5 minutes. Place over an ice bath. Stir occasionally for 30 minutes or until cool.
Meanwhile, for the blueberry ice-cream, place the blueberries, honey and lemon juice in a saucepan over medium-low heat. Cook, stirring, for 2 minutes or until honey dissolves. Simmer for 8 minutes. Transfer ? cup blueberry mixture to a bowl and reserve. Simmer remaining mixture for 2 minutes or until thickened. Set aside to cool.
Place the fig and reserved blueberry mixture in a food processor. Process until smooth. Press through a fine sieve set over a bowl. Discard solids. Stir in 600ml chilled coconut mixture. Place blueberry ice-cream and coconut ice-cream mixtures in fridge for 3 hours to chill.
Churn coconut ice-cream mixture in an ice-cream machine for up to 40 minutes or until thick. Spoon half the ice-cream into the prepared pan. Working quickly, spoon the thickened blueberry mixture over top of the ice-cream. Use a knife to create a swirled effect. Spoon over the remaining coconut ice-cream. Place in the freezer for 4 hours until firm.
Churn blueberry ice-cream mixture in ice-cream machine for ?40 minutes or until thick. Spoon over coconut ice-cream. Smooth surface. Cover with plastic wrap. Place in freezer for 8 hours until firm.
Place pan in fridge for 20 minutes to soften slightly. Turn cake onto a serving plate. Top with figs and blueberries. Drizzle with extra honey and sprinkle with cachous, if using.