It is currently lilikoi (passionfruit) season in Hawai'i, although it is getting close to the end - as of yesterday, Kokua Market still has some for sale (the farmers markets may have vendors selling the fresh fruit as well). I have been hoarding lilikoi pulp for months, getting fruit from my Mom Mom in Makaha and my hanai Mom in Manoa. Most of it got used for the wedding, but I do have some still stashed away. It won't last long, though. I've got a couple more recipes using lilikoi juice that are too good to save for special occasions!
Vegans: I'm working on a vegan lilikoi cupcake filling, and I'll post it when I get results I like. [update: never figured out a good curd, but now I have a jelly recipe using Pomonas Universal pectin - vegan and gluten-free - Lilikoi Lovers Passionfruit Jelly]
You really should use the freshest possible lilikoi juice for these recipes. About 5 - 6 fruits yield what I need for this curd recipe - I just cut them open (a serrated knife, like a breadknife or steak knife, works really well) and press the pulp through a mesh strainer. For a higher yield, heat the pulp up first, or give it a quick whirl in a food processor. If you have a Vitamix, you can blast the pulp, seeds and all, until smooth. This does NOT work well with a standard household blender - the broken seed pieces can be small enough to pass through a mesh strainer and still large enough to have jagged edges and be unpleasant to eat. The whole seeds are edible and in theory you could just leave them in - I did not want anyone at the wedding to bite into a cupcake and be alarmed by black spots in the center, though. If you can't get fresh, you can try frozen pulp (like Goya brand, available at many Latin/Hispanic markets) or Dafruta brand unsweetened passionfruit juice concentrate (also available in Latin/Hispanic markets - do not dilute, use it full strength. Mercado de la Raza in Honolulu carries it).
Lilikoi Curd Filling
makes about 2 cups [480 mL] - enough to ﬁll a 9" [23 x 3.5-centimeter] 3-layer cake or about 24 cupcakes
1/3 cup [70 grams] unsalted butter, at room temperature
3/4 cup [150 g] sugar
4 - 5 large egg yolks (4 for a softer, sauce-like curd, 5 for a thicker curd)
1 cup [250 mL] fresh lilikoi (passionfruit) juice
1 Tbs [15 mL] lemon juice (optional)
1/2 tsp [not sure how to convert this - a big pinch?] lemon zest (optional)
Cream butter and sugar together. Add remaining ingredients and blend. In a bain-marie (metal bowl set over pot of simmering water) or a double boiler, whisk frequently until
curd reaches 160 °F [71 ℃] (10 - 15 minutes). Curd will thicken further as it cools. Pour into bowl and press plastic wrap [cling ﬁlm] onto surface so "skin" will not form. Refrigerate until completely cooled before using. Use within 3 - 5 days. Keep refrigerated.