Cut the chicken breast into 2.5cm cubes or strips and place them in a large bowl. Season them with salt. Keep them at room temperature while you prepare the rest of the ingredients.
Slice the button mushrooms into 3 slices each (cut smaller ones in half).
Peel and finely chop the onion and mince the garlic cloves.
Heat a large skillet pan over medium-high heat. When it's hot, add 1 tablespoon of olive oil and brown the chicken cubes in batches, without overcrowding the pan. Use tongs or a silicone spatula to turn the cubes for even browning. Transfer them to a bowl and repeat with the remaining chicken, adding more olive oil as needed. Transfer all cooked chicken to a plate or bowl and set aside.
Reduce the heat of the pan and add another tablespoon of olive oil. Add the chopped onion, season with a pinch of salt, and sauté until it becomes translucent, about 3 minutes. Use this time to scrape the bottom of the pan to release any flavorful bits.
Add the garlic and sauté for 1 more minute to release its fragrance.
Stir in the tomato sauce, Worcestershire sauce, mustard, ketchup, and brandy mixing thoroughly to let the alcohol evaporate.
Return the browned chicken to the pan, Add the fresh cream, and mix well. Season with salt and pepper to taste. Let it simmer over medium heat for about 10 minutes, stirring occasionally, until it thickens.
Add the sliced mushrooms and cook for an additional 2 minutes until they become slightly tender.
Serve hot, traditionally with white rice and shoestring potatoes.