Prepare grill or broiler.
Place bread on a grill rack or baking sheet; cook 1 minute on each side or until toasted.
Place mushrooms in a food processor; pulse 10 times or until finely chopped.
Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add mushrooms and garlic; sauté 10 minutes or until most of the liquid evaporates. Add parsley and remaining ingredients; cook 2 minutes, stirring occasionally. Spoon 1 tablespoon duxelles onto each bread slice. Serve immediately.