1Heat oven to 350°F. Place paper baking cup in each of 18 regular-size muffin cups; spray paper cups with cooking spray.
2In large bowl, stir Bisquick mix, milk, sugar and eggs just until dry ingredients are moistened. In small bowl, mix peanut butter and vanilla just until blended; stir in chocolate chips. Stir into batter. Divide batter among muffin cups, filling each two-thirds full.
3Bake 24 minutes or until lightly browned. Remove from pan to cooling rack. Serve warm.