Prepare a grill for medium heat. Whisk lime juice, fish sauce, sugar, and 1 Tbsp. water in a small bowl until sugar is dissolved. Stir in garlic and cilantro stems; set nuoc cham aside.
Place pork on a rimmed baking sheet and season generously on both sides with salt and pepper, then drizzle with oil and turn pork to coat. Grill, turning often and moving around on grill to prevent flare-ups, until lightly charred all over and an instant-read thermometer inserted into the center registers 140° for medium), 12–15 minutes. Transfer meat to a cutting board and let rest 10 minutes before slicing.
Spoon some of nuoc cham over pork and top with cilantro leaves. Serve remaining sauce alongside.
Combine the milk, sugar, cinnamon stick, vanilla bean seeds and vanilla bean pod in a medium size saucepan over medium low heat. Whisk together and heat it until it is very hot, but not boiling. This should take about 5 minutes.
While the milk is warming, add the egg yolks to a large mixing bowl and whisk them vigorously, for 2 minutes, until they are lighter in color.
Remove the cinnamon stick and vanilla bean pod from the hot milk and discard. Place the whisked eggs next to the stove and slowly drizzle in about 1/3 cup of the hot milk while constantly whisking.
Repeat with another 1/3 cup of the hot liquid. When this is mixed in, slowly pour the egg mixture into the saucepan with the remaining milk, while stirring with a spoon. Stir and cook it for about 2-3 minutes, until the liquid is thick enough to coat the spoon.
Set a mesh strainer over a glass bowl and carefully strain the custard. Add the heavy cream and the ground cinnamon to the bowl and stir it together. Chill in the refrigerator for at least an hour, preferably until it is cool.
Pour into the ice cream machine and process according to your machine’s instructions. When the ice cream is finished it will be soft serve consistency. Transfer to a freezer-safe container and chill for a few hours for firmer ice cream. Enjoy!