Pat the chicken thighs dry and season both sides generously with salt and pepper.
Melt 2 tablespoons butter in a large skillet over medium-high heat. Sear the chicken 5–6 minutes per side, undisturbed, until golden and internal temperature reaches 165°F. Remove to a plate and tent with foil.
Bring a large pot of well-salted water to a boil. Cook the egg noodles according to package instructions, about 6–8 minutes, until just tender. Drain and set aside.
In the same skillet over medium heat, melt 1 tablespoon butter into the browned bits left behind. Add garlic and cook 30 seconds until fragrant.
Pour in the chicken broth, scraping the pan bottom to release the fond. Simmer 3–4 minutes until reduced by about a third.
Stir in the heavy cream and lemon juice. Simmer 1–2 minutes until the sauce coats the back of a spoon. Taste and adjust salt.
Add the drained noodles to the skillet along with 2 tablespoons butter. Toss until evenly coated in the sauce.
Nestle the chicken back into the skillet on top of the noodles for 1 minute to rewarm and glaze.
Scatter with fresh parsley and serve immediately.