Heat olive oil in large skillet over medium heat. Add mushrooms; cook for two minutes. Add garlic and rosemary; season with salt and pepper. Cook, stirring, for two minutes. Stir in veal demiglace. Cook until thickened. Toss with pasta. Serve immediately, garnishing each serving with parsley and one whole cleaned fresh mushroom. Serve with grated Parmigiano, if desired.