Freeze meat 15 minutes. Remove from the freezer and slice thinly across the grain. Set aside
Bring broth to a boil with the lemongrass. Add soba noodles and cook for 3 to 4 minutes. Remove noodles from the broth and distribute between 4 bowls.
Add mushrooms, sirloin, Thai chile pepper and spinach to the broth and cook for 3 minutes. Distribute broth and ingredients between bowls. Sprinkle with grated ginger, turmeric, and garlic. Garnish with scallions and additional Thai chile if desired.
I let the soup sit for about 5 minutes before serving.
This recipe was calculated using the exact brands and measurements I used to make this recipe. If you are following a strict diet please note changing anything will cause the nutritional info to change. My calculations are intended as a guide only.