Place the mushrooms in a food processor; pulse 10 times or until finely chopped.
Place minced garlic, parsley, and oil in a large nonstick skillet; cook 30 seconds over medium-high heat.
Add mushrooms; cook 6 minutes or until liquid evaporates and mushrooms are tender, stirring constantly.
Remove from heat; stir in salt and pepper. Cool slightly.
Lightly coat both sides of bread with cooking spray.
Heat a grill pan over medium-high heat; add half of bread. Cook 1 minute on each side or until toasted. Rub 1 side of each bread slice with cut sides of garlic clove halves. Repeat procedure with remaining bread and garlic. Spoon about 2 tablespoons mushroom mixture over each bread slice, and top with about 2 teaspoons cheese.