1Heat oven to 375°F. Place paper baking cup in each of 10 regular-size muffin cups.
2In medium bowl, stir 1 1/4 cups Bisquick mix and the brown sugar with whisk. Make well in center of mixture. In small bowl, stir milk, butter, vanilla and egg with whisk until well blended. Add to dry ingredients, stirring just until moistened. In small bowl, lightly toss diced strawberries and 1 teaspoon Bisquick mix. Stir into batter; spoon batter evenly into muffin cups.
3Bake 10 minutes. Place 1 strawberry slice on top of each muffin. Bake 8 minutes longer or until lightly browned. Cool 5 minutes. Remove from pan to cooling rack. Serve warm.