Preheat oven to 350 degrees. Butter a cookie sheet and set aside. In a large mixing bowl, whisk together brownie mix, flour, brown sugar and salt. Add in eggs and milk and stir with a large spoon. Add in melted butter and vanilla and stir until well blended. Spoon dough by heaping tablespoonfuls onto greased cookie sheet (you can fit 12 per sheet). Bake for 10 minutes. Remove from oven and allow to cool completely before frosting. Once cool, frost each cookie and sprinkle with chopped Oreos.
Vanilla Cream Frosting
In a large mixing bowl, with an electric mixer, whip together sugar, butter and cream until fluffy. Stir in vanilla and salt, blend well.