Preheat oven to 500°.
Combine first 4 ingredients, tossing to coat. Divide pear mixture evenly among 4 (8-ounce) ramekins; drizzle each serving with 1 tablespoon Marsala. Spoon 1 tablespoon crumbs over each serving; top each serving with 1 teaspoon butter.
Bake at 500° for 8 minutes or until filling bubbles and topping browns. Top each serving with 1/3 cup frozen yogurt.