Cut chicken breast into cubes and place in a small bowl. Season with salt and pepper.
Heat olive oil in a large skillet over medium-high and cook the chicken until nicely browned. You may need to brown the chicken in batches so as to not overcrowd the pan. Use more olive oil or butter as needed to brown all the chicken. Reserve cooked chicken.
In the same pan as the chicken, reduce heat add a bit more olive oil to the dripping and saute the onion and mushrooms until fragrant and translucent, about 3-4 minutes. Add the garlic and saute another 1-2 minutes.
To this mixture add the tomato sauce, ketchup, mustard, Worcestershire sauce and combine well. Add back the cooked chicken and incorporate. Adjust the seasoning with more salt and pepper as needed.
Reduce the heat to low and slowly add the heavy cream. Mix well and let simmer for a few minutes until the mixture begins to thicken a bit. Stir occasionally during this time. Adjust liquid with water or chicken stock. The mixture should not be too dry or too soupy.
Garnish with chopped parsley and potato sticks to taste.
Traditionally served with fresh cooked white rice