Season the sliced veal with salt and black pepper.
In a large skillet, heat the butter and vegetable oil over medium-high heat.
Add the veal strips in batches, cooking until they are just browned on all sides. Remove the veal from the skillet and set aside.
In the same skillet, add the finely chopped onion and sauté until it becomes translucent, about 5 minutes.
Add the minced garlic and cook for another minute until fragrant.
Add the sliced mushrooms to the skillet and cook until they release their moisture and become golden brown.
Pour in the dry white wine to deglaze the pan, scraping up any browned bits from the bottom.
Let the wine simmer for a few minutes until it reduces by half.
Stir in the heavy cream and beef or veal broth. Bring the mixture to a gentle simmer.
If you prefer a thicker sauce, mix the cornstarch with water to make a slurry and stir it into the sauce. Cook for a few more minutes until the sauce thickens.
Return the browned veal strips to the skillet and stir to coat them with the sauce.
Cook for another 2-3 minutes until the veal is heated through and tender.
Transfer the Zürcher Geschnetzeltes to serving plates.
Garnish with freshly chopped parsley and a sprinkle of lemon zest if desired.
Enjoy your meal!