Make sure the molds are prepared before making the cream.
Whip the heavy cream to medium peaks and reserve in refrigeration.
Combine the yuzu juice, sugar, and eggs in a bowl and cook over a hot water bath until thickened.
Take off the heat and stir in the butter; dissolve completely.
Add the bloomed gelatin to the above mixture while it is hot so that it dissolves completely.
Fold in one-quarter of the cold whipped heavy cream. Then fold in half of the remaining whipped cream and then the other half of the whipped cream. Pour into a piping bag and pipe into the cake molds all the way to the top.
Even out the top with an offset spatula.
Freeze and reserve leftover yuzu cream. At this point, the cream will dip inside the mold. It always happens, which is why I prefer to assemble cakes upside down. Once the cake is frozen, pour some yuzu cream on top of the cake and even it out again. This will correct the dip in the cake.