Whisk together sugar, yolks, and egg. Set aside.

In a heavy bottomed nonreactive medium sauce pot, gently heat passion fruit puree, butter, and salt over low heat until butter has melted.

Remove pot from heat and whisk a few tablespoons of the melted mixture into the egg mixture. Continually whisking, continue to add a few tablespoons of hot mixture into eggs at a time.

Pour all the mixture back into the pot. Set over medium heat. Use a wooden spoon or sturdy spatula to continually stir mixture, making sure to scrape the bottom and edges of the pot to prevent eggs from curdling or scrambling.

Cook for about 5-8 minutes until mixture has thickened to nappé consistency and has reached a temperature of 160°F.

Remove from heat and strain curd through a fine mesh sieve/strainer into a medium bowl.

Cover with plastic wrap, allowing the wrap to lay directly on the surface of curd. Chill in the fridge for at least 2 hours to thicken and cool.

For Indirect Heat/Double Boiler Method: Fill a medium sauce pot with about 2-inches of water. Bring to a simmer. Set a glass bowl over the pot, making sure the bottom of the bowl does not touch the water.

Add sugar, yolks, egg, and passion fruit to bowl. Whisk until eggs are incorporated. Add butter and salt. Continue to gently heat until butter has melted, stirring occasionally.

Once butter has melted, change to a wooden spoon or spatula. Continually stir mixture for about 8-10 minutes, until it has thickened to nappé consistency and has reached a temperature of 160°F.

Remove from heat and strain curd through a fine mesh sieve/strainer into a medium bowl.

Cover with plastic wrap, allowing the wrap to lay directly on the surface of curd. Chill in the fridge for at least 2 hours to thicken and cool.