Prep: 15 minutes; Cook: 45 minutes; Total Time: 1 hour.
1. Coat a 12-cup muffin tin with cooking spray; set aside.
2. Heat butter in a 4- to 5-quart pot over medium heat until melted; add onion and next 5 ingredients (through pepper). Cook until softened (about 5 minutes), stirring occasionally. Add mushrooms; cook over medium-high heat until mushrooms are tender and liquid evaporates (about 5 minutes), stirring well. Add broth; simmer.
3. Preheat oven to 425°. Remove pot from heat; stir in remaining ingredients with a fork. Cover and let stand 5 minutes. Spoon stuffing mixture into 10 cups of prepared muffin tin in mounds; bake in middle of oven until golden on top (about 25 minutes). Let cool in oven at least 15 minutes; remove from tin.