Freeze a 8 1/2 x 4 1/2-inch loaf pan and a serving platter.
In a medium saucepan, whisk together the passion fruit juice and cornstarch. Bring to a rolling boil over medium-high heat and whisk continuously. You want to continue cooking it for about 1 minute after it starts to boil to cook out the starch. It will be slightly thickened.
Reduce the heat and add the sugar, half and half, cream and salt. It will thicken slightly due to the acid in the juice. Cook slowly just until it starts to bubble on the edges of the pan, but don't bring it back to a boil.
Pour the ice cream base into a shallow dish, cover and refrigerate until well chilled, about 3 hours. This can be done a day ahead.
Freeze the ice cream according to your Ice Cream Maker instructions. Empty the ice cream into the frozen loaf pan. Smooth the top, cover with plastic and return it to the freezer until well chilled, about 5 hours or overnight.
When the ice cream is well set, it is time to unmold it onto the frozen serving platter. Fill a 9 x 5-inch loaf pan with 1/2 inch of hot water.
Lower the loaf pan filled with ice cream into the hot water for just a few seconds.
Unmold it onto the frozen platter. If it doesn't slip out easily, just run a butter knife around the edge and try again. Freeze the ice cream while you make the meringue.