In a resealable plastic bag, combine the beef, 1 tbs oil, 1 1/2 tsp fish sauce and salt. Seal bag and mush it around with your hands to distribute the marinade evenly. Set aside at room temperature for 15 minutes.
Cook the noodles
Over medium high heat, combine the broth, ginger, and the remaining 2 tsp. fish sauce in a large sauce pan and bring to a boil. Reduce heat to low, cover and simmer for 30 minutes.
Bring a large pot of water to a boil over high heat. Add noodles and cook just until tender, according to the package instructions. Drain, rinse under running cold water and divide evenly to 4 bowls.
Add remaining 1 tbs oil into pan over high heat. Add beef and cook until seared on both sides, about 4 minutes total. Transfer to a plate.
Strain the broth, return to the saucepan and bring to a boil over medium-high heat. Add basil and beef and cook for about 3 minutes. Ladle over the noodles and serve hot!