Line an 8-inch square baking pan with parchment paper, leaving overhang on two sides. Lightly grease the parchment.
Add the passionfruit puree to a small saucepan and simmer over medium heat until reduced to ½ cup, about 10 to 15 minutes.
Add the heavy cream, butter, and sweetened condensed milk to the reduced puree. Warm over low heat until the butter melts and the mixture is smooth. Keep warm.
In a large heavy-bottomed saucepan, combine the sugar, corn syrup, water, and salt.
Cook over medium heat without stirring until the mixture turns a light amber color. Gently swirl the pan occasionally for even caramelization.
Slowly whisk the warm passionfruit mixture into the caramelized sugar. The mixture will bubble vigorously.
Continue cooking, stirring constantly, until the caramel reaches 244°F on a candy thermometer.
Remove from the heat and stir in the vanilla extract.
Pour the caramel into the prepared pan and smooth the surface.
Cool completely at room temperature for 4 to 6 hours.
Lift the caramel from the pan using the parchment overhang.
Cut into 36 squares and wrap individually in wax paper.