Preheat oven to 375°F (190°C).

Coat 10 muffin tins with baking spray or line cups with liners.

In a large bowl, combine all-purpose flour, whole wheat flour, Splenda or Stuvia, baking powder, salt, baking soda, and cinnamon.

In a small bowl, whisk together the vanilla yogurt and egg.

Gently fold the yogurt-egg mixture into the dry ingredients until just combined.

Fold in the melted butter, chopped peaches, half and half, and blueberries.

Divide the batter evenly among the muffin cups.

In a separate small bowl, mix together brown sugar and cinnamon for the topping.

Cut in butter into the topping mixture until combined completely.

Sprinkle the topping evenly over the muffin batter.

Bake until golden brown and a toothpick inserted into the center of a muffin comes out clean, approximately 25-30 minutes.

Let the muffins cool in the pan for 5 minutes.

Flip the muffins out onto a wire rack and let cool for 10 minutes before serving.