We make 2 kinds of brownie mountains in our bakery. The Kids brownie mountain is made with cookies and crème whipped topping in the middle drizzled with hot fudge and white donut icing, a scoop of m&m's and oreos on top. The Sweet and Salty brownie mountain is made with vanilla whipped topping, hot fudge drizzle, caramel, chocolate curls, and pretzels.
They are popular because you have 2 rows of bite size brownies stacked up in a circle with the filling in the middle, you dip a brownie into the filling and eat it.