Chill food processor working parts in freezer for 10 minutes. Do the same with the shrimp.
Combine ground shrimp, pork, garlic, shallots, salt, fish sauce, sugar, pepper and rice powder in chilled food processor. Puree shrimp mixture, stopping to scrape down bowl with rubber spatula a few times, until it is a semi-smooth paste Mixture should gather into a single mass as it whips around in the processor.
Sautoé a 1tbsp. sample patty in a little oil until cooked through; taste and adjust seasoning as needed. Transfer mixture to container and refrigerate 30 minutes to allow mixture to set.
Drop tablespoon-size balls into the simmering broth to cook, about 3 minutes. Serve as a garnish for noodle bowl soups.
On one of my routine morning adventures, I stumbled upon this street vendor selling Bún Bò Huế for breakfast. It was 7 a.m. and I was really hungry.