Cut baguette into 4 (1-inch thick) slices and 8 (1/4 inch thick) slices and place on a baking sheet. Reserve remaining baguette for another use. Bake bread at 400 ° F for 5 minutes or until toasted. Set aside. Alternatively, toast in toaster oven.

Melt butter in a large skillet over medium heat; add onion, and cook, stirring often, 20 minutes or until caramel colored. Add mushrooms and garlic and cook, stirring constantly, 3 minutes. Stir in wine or broth; bring to a boil. Reduce heat and simmer, stirring occasionally, 20 minutes or until slightly thickened.

Stir together 1/2 cup water and flour until smooth. Stir flour mixture and pepper into mushroom mixture; cook, stirring constantly, 1 minute.

Place thick baguette slices in bottoms of 4 8-ounce custard cups or small ovenproof bowls. Spoon mushroom mixture evenly into cups. Top each with 2 baguette slices. Sprinkle evenly with cheese.

Bake at 350 ° F for 5 minutes or until cheese melts. Sprinkle with parsley.