Preheat oven to 400°F. Grease 12 large muffin cups or line with paper liners.

Combine Bisquick and sugar.

Beat together sour cream, milk, egg and apple.

Add to dry ingredients and stir only until combined.

Divide half of batter evenly into prepared muffin cups.

Combine ingredients of the streusel mixture and sprinkle over batter.

Top with remaining batter.

Bake in preheated 400°F oven for 20 min.

Serve warm.

If desired, dip tops in melted butter, then in a cinnamon/sugar mixture.

Makes 12 muffins.