To a medium saucepan, add the coconut milk. Heat slowly over medium heat, stirring often. DO NOT BOIL.
To a medium-sized bowl, add the eggs, and whisk vigorously until creamy and smooth.
When the coconut milk is very hot (not boiling), use a ladle to add a little at a time of the hot liquid to the eggs, whisking to incorporate. When the tempered eggs are warm, whisk them into the remaining hot coconut milk on the stove.
Continue cooking the custard - stirring constantly - until it is thick enough to coat the back of a spoon. This process will take about 6 to 8 minutes.
Pour the custard into a sealable container. Chill thoroughly. When the mixture is cold, add to a blender or food processor.
Add the coconut whipping cream or cream of coconut, the lucuma pulp, and the vanilla. Purée until very smooth. Taste for sweetness. Add corn syrup as needed.
Freeze according to manufacturer's instructions. I now have a compressor model, and it freezes in about 40 minutes if it starts out cold.
Serve immediately or store in an appropriate airtight container in the freezer. Garnish with candied pistachios if desired!