Apple Cinnamon Muffins- Yum!!

This is my favorite thing to make for breakfast when my family is in town. (Which they were on Monday.) It's quick, super easy, and very tasty.
Got this recipe from a friend. I tweaked it a tad, here's my version.

Preheat oven to 375 degrees.
3/4 c. white flour
3/4 c. whole wheat flour
1/2 c. sugar
1 1/2 t. baking powder
1 t. cinnamon
1 egg beaten
1/3c. melted butter
1/2 c. milk
1c. chopped apple
1/2 c. chopped toasted walnuts

Not shown in this picture, but I also like to put a crumb topping on these:
CRUMB TOPPING
1/4 c. chopped walnuts
1/2 c. flour
2 T sugar
2 T brown sugar
2-3 T melted butter
Mix together and put on top of muffins before you bake them.

Mix all ingredients. Put in greased muffin tin or use muffin liners.
Bake 18-23 minutes. Let stand 5 minutes. Enjoy some delicious warm muffins with a big cup of coffee.