Preheat oven to 425 degrees F. Note: You will bake the muffins at 425 for the first five minutes, then reduce the heat. Line 18 to 20 muffin cups with paper liners.
Whisk together the flour, baking powder, baking soda, salt and sugar in a large mixing bowl.
In a second bowl whisk together the egg, yolk, sour cream, milk and vanilla until smooth.
Pour the milk mixture into the flour mixture and stir until almost fully blended, then pour in the melted butter and stir until everything is evenly blended.
Stir in the white chips, then carefully stir in the raspberries.
Divide the batter equally among the muffin cups and sprinkle tops with sugar.
Bake at 425 for 5 minutes.
Reduce oven heat to 350 and bake for about 20 more minutes.
Allow the muffins to cool completely before serving. These muffins, in my opinion, are better after they’ve sat around for an hour or two.