Set Sous Vide to 158F
Heat large skillet over medium-high heat for one minute. Add sesame and olive oils and heat until shimmering.
Add onions, stir to combine. Sauté for 5 minutes, stirring frequently until onions have softened and lightly browned.
Add garlic and continue to cooking until onions are caramelized.
Remove from heat. Add ginger and stir.
Add hoisin sauce, fish sauce, and water to the pan. Stir to combine.
Add sriracha to taste.
Place pork in a ziplock bag or vacuum seal bag with onion and hoisin mixture. Seal the bag for sous vide.
Place pork bag in water bath and set timer for 24 hours. Cover water bath with plastic wrap to minimize evaporation. Add water intermittently to keep the pork bag submerged. A large binder clip is helpful to keep the bag in place.