Bring a medium pot of lightly salted water to boil for pasta.
Place cut chicken thighs in a medium bowl and sprinkle with flour, salt, pepper, and paprika. Toss until the chicken is well-coated.
In a large skillet, melt 2 tablespoons of the butter over medium-high heat. Add the chicken to the pan and spread it out in a single layer. (Discard any flour that is left in the bowl.)
Cook the chicken undisturbed for 2 to 3 minutes until the bottom of the chicken is golden brown. Give everything a good stir, turn the heat down to medium, and continue to cook the chicken, stirring occasionally, until the chicken is cooked through, about 2 to 4 minutes.
Transfer the cooked chicken to a clean bowl or plate and return the skillet to medium heat. Add the remaining 2 tablespoons of butter. Once the butter is melted, add the onions, garlic, and mushrooms. Cook for 5 minutes, until the onions and mushrooms begin to soften. Use a wooden spoon to stir occasionally, scraping any cooked-on bits from the bottom of the pan as you go.
To the pot of boiling water, add egg noodles and cook according to package instructions. Drain and set aside.
While your pasta cooks, into the skillet of onions and mushrooms, stir the tomato paste and thyme and cook for 1 minute.
Stir in the chicken broth, sherry, and lemon juice. Bring to a simmer, and cook for 5 minutes, and then add the chicken back to the pan and simmer for 1 minute more, until chicken is heated through.
Remove the pan from heat and stir in the sour cream.
Serve sauce over the egg noodles and enjoy!