Bring the coconut milk, lemongrass, vanilla, stevia and lime zest to a simmer in a medium pot.
Simmer for 20 minutes, then add the erythritol and simmer for another 10 minutes.
Temper your egg yolks by removing some of the hot liquid and transferring it to a small bowl. Slowly whisk in the the yolks, and then slowly whisk that mixture back into the pot of simmering coconut milk.
Remove from heat and allow to cool almost completely.
Transfer to ice cream machine and process to manufacturer's directions for your particular ice cream maker.
Serve with chopped peanuts sprinkled over the top.