Preheat oven to 350 degrees.
Beat 1/2 c brown sugar, 1 egg, and 1/8 t salt with an electric mixer until blended.
Stir in chocolate chips, walnuts, and 1/2 t vanilla.
Set aside.
Beat remaining 1/2 t vanilla, butter, 1/3 c sugar, and 1/3 c brown sugar until creamy.
Add 1 egg and beat until blended.
Combine flour, soda, and 1/2 t salt. Stir into butter mixture.
Place paper baking cups into mini muffin pans and coat with cooking spray.
Spoon 1 1/2 t batter into each cup.
Bake for 12 minutes.
Spoon chocolate chip mixture over cupcakes and bake 10 more minutes.