1. Preheat oven to 350 degrees.
2. Combine the first 5 ingredients in a large mixing bowl.
3. Sift the next 5 (dry ingredients) into this bowl, and stir to combine (do not over-mix, or brownies wil be tough!).
4. Gently fold in chips and nuts.
5. Bake in a greased 9-inch square baking pan for 20-25 minutes, or until toothpick inserted in center comes out clean.
6. Cool on a wire rack.
7. For frosting, beat cream cheese, butter, and confectioner's sugar in a small bowl until light and fluffy.
8. Add cinnamon, vanilla, and enough milk to achieve desired consistency. Spread over cooled brownies.
9. Store in refrigerator.