Stuffed Mushrooms

18 large mushrooms
1 tablespoon olive oil
1/4 cup onion, minced
1 clove garlic, minced
1/4 cup walnuts, finely chopped
1 shredded wheat biscuit, crushed
1 tablespoon Parmesan cheese, grated
pepper to taste
1/2 teaspoon paprika
1/8 teaspoon basil
1/8 teaspoon parsley
1/8 teaspoon oregano