In a small mixing bowl, combine beaten egg yolks with salt; set aside.
In a medium saucepan, combine sugar and cornstarch. Add half-and-half and whisk until smooth. Turn the heat to medium.
When the mixture gets pretty warm, temper the eggs by slowly pouring the milk mixture over the yolks, whisking constantly. After a couple of ladles, pour yolks into the saucepan, whisking continuously.
Add lemongrass and ginger; whisk vigorously. To this, add lemon zest and lemon juice; whisk until the pudding thickens, about 3 minutes.
Remove from the heat and whisk in butter.
Pour the mixture through a sieve over a measuring cup. Using a spatula, scrape the thick pudding through the screen; discard the solids.
Pour the filling into the prepared Chocolate Honey Graham Cracker Pie Crust and level it out. Cool to room temperature before decorating it if desired, about 2 hours.
Transfer to the fridge at least 3 hours to chill.