To make the caramel and Beurre Bordier Demi-Sel ice cream: In a saucepan over high heat, combine the cream, Beurre Bordier Demi-Sel and sugar. Bring the mixture to 170°C (this will produce a deep amber caramel). Drizzle the milk off the heat, to avoid burning yourself with the fumes and caramel.
In a saucepan, boil the cube in 1L of water and leave to simmer throughout the preparation. Peel and slice the onion and sauté in a frying pan over high heat with a drizzle of olive oil until lightly colored.
To make the lemon yuzu cream: Bring the lime juice and gelatine to the boil in a saucepan. Whisk the eggs with the sugar in a mixing bowl, then pour in the boiled lemon juice. Whisk briskly for 3-4 minutes. Pour the cream back into the bowl. When lukewarm, fold in the finely diced Bordier Yuzu Butter.