In a large skillet, heat vegetable oil over medium-high heat. Add the sliced veal and cook until browned. Remove the veal from the skillet and set it aside.

In the same skillet, melt butter and sauté chopped onion until translucent. Add sliced mushrooms and garlic, and cook until the mushrooms are tender and slightly browned.

Sprinkle flour over the mushrooms and stir well to combine. This will create a roux that thickens the sauce.

Gradually pour in beef broth while stirring continuously to avoid lumps. Let the mixture simmer until the sauce thickens.

Return the cooked veal to the skillet and stir in the Dijon mustard. Season with salt and black pepper to taste.

Reduce the heat to low and stir in sour cream. Simmer gently for a few minutes, ensuring not to boil the sour cream.

Serve the stroganoff veal over cooked egg noodles or rice, garnished with freshly chopped parsley.