Heat 1 ½ tablespoons oil in a large sauté pan over medium high heat. Season the chicken pieces with ¼ teaspoon salt and ⅛ teaspoon pepper and sprinkle them with flour. Toss to coat all of the pieces. Add the chicken to the pan in a single layer and cook without moving until golden, 3-4 minutes. Flip the pieces over and cook another 2-3 minutes on the other side (the chicken will finish cooking later in the sauce). Remove chicken from the pan.

Whisk the tomato paste and chicken stock together in a bowl. Set aside.

Heat the remaining ½ tablespoon oil in the pan and add the onion. Cook 2-3 minutes until it starts to soften and then add the garlic and mushrooms. Cook, stirring occasionally, until vegetables are tender, 4-5 minutes. Add the chicken back to the pan along with the paprika and stir to combine well. Turn the heat up to high and add the sherry or wine (if using). Cook until reduced. Pour in the tomato paste and chicken stock mixture and season the sauce with the remaining ¼ teaspoon salt and ⅛ teaspoon pepper. Simmer a few minutes until the sauce starts to thicken and the chicken is cooked through. Turn the heat off and stir in the sour cream or yogurt.

Serve the chicken over egg noodles. Sprinkle with parsley before serving.