Apple Walnut Muffins with Streusel Topping

I was looking for something different to have for breakfast today and I had a lot of green apples in my refrigerator. Does anyone know why I have so many green apples at my house?  I found this recipe at foodnetwork.com and other than the apple peeling and chopping it only took a few minutes to make. 

Ingredients:
1-1/2 cups all purpose flour
1 tsp baking powder
1/2 tsp baking soda
1/4 tsp salt
1 tsp ground cinnamon
1/2 tsp nutmeg
2 large eggs
1/2 cup sour cream or buttermilk
4 tbsp melted unsalted butter
1 cup packed brown sugar
1 cup peeled, cored and chopped green apples
1/2 cup chopped walnuts

Streusel Topping:
1/4 cup plus 1 tbsp finely chopped walnuts
1/4 cup plus 1 tbsp packed brown sugar
2 tbsp all purpose flour
1/2 tsp ground cinnamon
2 tbsp melted unsalted butter

Directions:
Preheat oven to 375 degrees.  Line a 12 cup muffin tin and set aside. 

In a large bowl, sift together flour, baking powder, baking soda, salt, cinnamon and nutmeg.

In another bowl whisk together the eggs, sour cream and melted butter. Add sugar and beat to combine. Add the dry ingredients and mix until just combined. 

Fold in apples and walnuts.  Divide the batter among the muffin tin cups, filing each about 2/3 full.

In small bowl combine walnuts, brown sugar, flour, cinnamon and melted butter for streusel topping.

Sprinkle about 1 tbsp of the crumb mixture over the top of each muffin.  Bake until tester inserted into muffin comes out clean, about 24 minutes.  Remove from oven and let sit in muffin tin for 10 minutes.  Let cool slightly before serving. 

Enjoy!  Susan