Shrimp in Champagne Sauce with Pasta

1 cup sliced mushrooms
1 tablespoon olive oil
3/4 pound medium shrimp, shelled
1 1/2 cups champagne
1/2 tablespoon garlic pepper seasoning
2 tablespoons minced shallots or scallions
1 large tomato, diced
1 cup heavy cream
1/2 pound dried thin spaghetti
3 tablespoons chopped parsley
Grated Parmesan cheese

Saut