Cook the noodles. Bring a large pot of salted water to a boil and cook the noodles according to package directions. Before draining, scoop out ½ cup of the pasta water and set aside. Drain and set the noodles aside.
8 oz soba noodles
Brown the beef. While the noodles cook, heat a large skillet over medium heat and add the ground beef. Let it cook undisturbed for a minute or two to develop a nice brown crust before breaking it up into small chunks.
1 lb ground beef
Build the flavor. Add the minced garlic, ginger, and red pepper flakes (if using) to the beef and stir to combine. Sprinkle in the coconut sugar and gently stir until everything is evenly coated.
4 garlic cloves, 1 teaspoon grated ginger, 1 teaspoon red pepper flakes
Add the sauce. Pour in the beef broth, coconut aminos, hoisin sauce, and rice vinegar, stirring to combine. Sprinkle the arrowroot starch over the top and stir it into the mixture. Let the sauce simmer for 2 - 3 minutes, or until it begins to thicken.
½ cup beef broth, ¼ cup coconut aminos, 2 tablespoon hoisin sauce, 2 tablespoon rice vinegar, 1 ½ tablespoon coconut sugar, ½ tablespoon arrowroot starch
Bring it all together. Stir in the reserved pasta water and let the sauce simmer until glossy and thick enough to coat the back of a spoon. Add the cooked noodles to the skillet and toss until every strand is coated.
½ cup reserved pasta water
Serve. Divide the noodles into individual bowls and top with chopped green onions and a drizzle of chili oil.
3 green onions, 1 teaspoon chili oil