Asiago Dip with Crostini

1 cup mayonnaise*
1/2 cup finely chopped red onion
1/2 cup grated Asiago or Parmesan cheese
1/2 cup finely chopped fresh mushrooms
8 oz sour cream*
Loaf French bread
1/4 cup sun dried tomatoes, rehydrated and finely chopped

Preheat oven to 350F. Combine all ingredients but the bread, spoon into a 1 quart casserole. Bake at 350F for 30 minutes or until hot and bubbly. If top starts to get to brown, cover the dish. Slice French bread in half lengthwise and cut into 1/2-inch thick slices. Place on cookie sheet and bake in oven until toasted and hard. Serve dip with Crostini bread.

* Light mayonnaise and sour cream work fine for this recipe, but not fat-free