Pat the chicken breasts dry, cut into 2-inch cubes, and season with salt and pepper. Then follow the instruction according to the chosen cooking method below.
STOVETOP METHOD: In a large stainless steel pan, heat the 2 tablespoons of olive oil and melt 2 tablespoons butter over medium heat. Add the mushrooms and cook until they are browned and cooked through, about 5 minutes. Remove from heat and reserve.
Add 3 tablespoons oil and increase the heat to medium-high. Pan-fry the cubed chicken in batches so that it is browned on all sides (about 3-5 minutes), then let rest on a plate or bowl after pan-frying. Lower the heat to medium and add 1 tablespoon of oil and the onions, cooking and stirring occasionally until they are soft (about 3 minutes).
Add the garlic and cook until soft and fragrant, about 1 minute. Return chicken to the pan! Pour in the wine and let cook until it has been almost fully absorbed. Stir in both the tomato sauce and the chicken stock/broth. Cook, partially covered, over medium-low heat for 15-20 minutes.
When the chicken is cooked, remove from the heat and fold in the mushrooms, heavy cream, mustard, and parsley. Taste and adjust the salt and pepper, if needed. Serve the Chicken Stroganoff with white rice and shoestring potatoes. Or, as a variation, serve with egg noodles.
SLOW COOKER/CROCKPOT: To make our Brazilian chicken stroganoff in the slow cooker, cook the mushroom, chicken, and onion/garlic in a pan as described in the STOVETOP METHOD. Place cooked onion, garlic, and chicken along with the wine, tomato sauce, and stock (use only 1 cup instead of 2) in the slow cooker.
Close the lid and cook on high for 4 hours. Then when the chicken is cooked, fold in the mushrooms, heavy cream, mustard, and parsley. Taste and adjust the salt and pepper, if needed.
INSTANT POT/PRESSURE COOKER: Press the sauté function and once your Instant Pot or Pressure cooker heats, cook the mushrooms, the chicken, and also both the garlic and onion as described in STOVETOP METHOD. Make sure to add only 1/2 cup of broth or stock instead of 2 cups. Lock the lid, seal the valve, and cancel the sauté function. Then press the poultry button and let it cook for about 15 minutes. Carefully turn the valve to release the pressure quickly, then remove the lid. Next, fold in the mushrooms, heavy cream, mustard, and parsley. Taste and adjust the salt and pepper, if needed.