In a medium bowl, toss the chicken with salt and pepper.
In a large nonstick skillet, heat the oil over medium. Add the onions; cook, stirring often, 3 to 4 minutes. Add the garlic; cook, stirring often, until soft, about 3 minutes. Add the flour and paprika; stir 1 minute to blend. Whisk in the stock; add the tomatoes. Reduce heat to medium- low; cover. Simmer, stirring often, until flavors meld, about 15 minutes.
Add the chicken; cook, stirring often, until the sauce thickens and the chicken is cooked through, 8 to 10 minutes. Let cool 5 minutes, then stir in the sour cream. Season.
While the chicken is cooking, bring a large pot of water to a boil. Salt the water, add the noodles and cook to al dente; drain. Divide among plates. Top with the paprikash and parsley.
