Peel and halve the onion, then cut into fine slices. Clean the mushrooms and cut into fine slices.
Heat oil in a deep pan over medium-high heat. Coat each chicken schnitzel in flour, shake off excess, and fry for 3 to 4 minutes per side until golden and cooked through to 74°C / 165°F internally. Transfer to a plate.
In the same pan, add the sliced onions and mushrooms. Fry over medium-high heat for 3 to 5 minutes until softened.
Add the white wine and simmer for 3 to 5 minutes until mostly reduced.
Pour in the sweet cream, salt, pepper, a pinch or less of garlic granules, the vegetable stock, and parsley. Stir to combine.
Return the cooked chicken schnitzel to the pan. Simmer on medium heat for 5 to 10 minutes until the sauce thickens slightly.