Apple streusel muffins

18    Regular muffins
 
  The delicious crumb topping makes these muffins taste
  like miniature coffee cakes. Good at tea time and also
  for brunch. Cool at least 1 hour before serving.
  
  Topping
  
  1/2 cup chopped walnuts 1/4 cup all-purpose flour 3
  tablespoons granulated sugar 2 tablespoons butter, at
  room temperature 1/4 teaspoon ground cinnamon
  
  Batter
  
  1 1/2 cups all-purpose flour 1/2 cup granulated sugar
  2 teaspoons baking powder 1 teaspoon ground cinnamon
  1/4 teaspoon baking soda 1/4 teaspoon salt 2 large
  eggs 1 cup sour cream 1/4 cup (1/2 stick) butter,
  melted 1 cup diced unpeeled apple, preferably a tart
  apple such as Granny Smith or Greenings
  
  Heat oven to 375 F. Grease muffin cups or use foil
  baking cups.
  
  Put streusel topping ingredients into a medium-size
  bowl. Mix with a fork, then crumble with fingers until
  mixture looks like chopped walnuts.
  
  To make the muffin batter, thoroughly mix fllour,
  sugar, baking powder, cinnamon, allspice, baking soda,
  and salt in a large bowl.
  
  Break eggs into another bowl. Add sour cream and
  melted butter, and whisk until well blended. Stir in
  diced apple.
  
  Pour egg mixture over flour mixture and fold in just
  until dry ingredients are moistened.
  
  Scoop batter into muffin cups. Top each muffin with
  about 2 teaspoons of the streusel topping.
  
  Bake 20 to 25 minutes, or until browned. A toothpick
  inserted into the center should come out clean. Remove
  from pans and let cool at least 1 hour before serving.
  
  Source: Muffins By Elizabeth Alston