Prepare the veggies (onion, garlic, and mushrooms). If you are serving this stroganoff over noodles, get water boiling for the noodles and prepare them according to package directions; don’t forget to generously salt the pasta water. I like stroganoff best over wide ribbon noodles.
Trim the fat from the chicken breasts, dab with paper towel, and cut into 1-inch, bite size pieces. Add chicken pieces to a bowl and toss with the Italian seasoning, garlic powder, paprika, salt, and pepper (I add 1 teaspoon salt and 1/2 teaspoon pepper), but add to personal preference (add less if chicken broth is salted). Toss chicken to coat in seasonings.
Heat the olive oil in a large skillet. Add the chopped chicken in a single layer and cook for 6–8 minutes or until cooked through (160°F and juices run clear). Stir the chicken often to ensure all sides are evenly cooked. Remove chicken to a large plate and tent with foil.
Don’t wipe out the skillet, since any browned bits will add lots of flavor! Add the butter, diced onion, and minced garlic. Cook for 3–5 minutes or until onion is translucent and fragrant. (Reduce heat if anything is burning or browning.) Add mushrooms and cook another 1–2 minutes. Stir in tomato paste and sprinkle the flour on top. Stir, cooking for 1 more minute.
Gradually stir in the chicken broth and the heavy cream, stirring constantly. Scrape the bottom of the pan to release any browned bits. Bring to a simmer, then reduce heat to medium low. Stir frequently and cook until slightly thickened, about 3–4 minutes.
Reduce heat to low. Add in the sour cream and Dijon mustard. Stir until smooth and incorporated.
Add the chicken (along with any juices accumulated on the plate) to the sauce. Stir until coated and warmed through, about 1 minute. Taste and adjust for any additional salt or pepper. You can also add some more Dijon here if desired.
Serve chicken and sauce over cooked, drained noodles. Sprinkle with fresh chopped parsley if desired.
Notes
Note 1: If serving Chicken Stroganoff over pasta, don’t forget to salt the cooking water! Salting is the only chance to season the actual pasta, or it can make the entire dish taste bland. (Read about how to how to salt your pasta water here.)Storage: Store leftovers in an airtight container in the fridge for up to 4 days. Reheat gently on the stove over low heat, adding a splash of broth if needed. Freeze for up to 3 months, but note the sauce may change texture.