Preheat oven to 350.

Combine brown sugar and butter in a medium microwave-safe bowl. Microwave on high in 30-second intervals, stirring after each interval, until butter is melted and sugar is dissolved. Allow mixture to cool completely before stirring in the eggs and vanilla. Set mixture aside.

In a large bowl combine the flour, baking powder, and salt, whisking well to combine. Add butter mixture to the flour mixture, and stir with a rubber spatula until ingredients are completely incorporated. (Batter will be very thick.) Pour batter into a greased 11x7" or 9x9" pan, and use a spatula to spread evenly. Sprinkle the chocolate chips, almonds and marshmallows evenly over the batter. Bake for 25 minutes, or until cookie layer is set and the marshmallows are toasted. (If you prefer the marshmallows to be less brown, the marshmallows can be added 10 minutes into the baking time instead of at the beginning.) Allow bars to cool for 15 minutes.

While bars cool, place dark chocolate melting wafers in a microwave-safe bowl. Microwave at 50% power in 30-second intervals, stirring after each interval, until chocolate is melted and smooth. Drizzle chocolate over the cooled bars before cutting into squares.