In a small bowl, whisk together the egg and lemon juice.
Heat the chicken broth in a pot over medium heat until it begins to boil.
Once boiling, add the egg noodles and cook until tender, about 5 minutes.
Turn off the heat, and while stirring the broth gently, slowly pour in the egg and lemon mixture. Whisk constantly to create silky egg ribbons.
Turn the heat back on and bring to a gentle boil for 1–2 minutes.
Turn off the heat and let the soup sit for a moment before serving.
Optional: Top with fresh parsley for color and a pinch of salt if desired.