Line baking sheets with parchment and preheat oven to 350 degrees F.
In large bowl, beat butter and brown sugar until fluffy. Add eggs and vanilla, and beat another 2-3 minutes, scraping sides of bowl.
In a separate bowl, whisk together flour, cocoa powder, hot chocolate mix, baking powder, baking soda, and salt. Add to butter mixture, and mix just until incorporated. Gently fold in chocolate chips and Mallow Bits. The Mallow Bits are fragile, so vigorous stirring will cause them to disintegrate.
Scoop dough by rounded tablespoons onto prepared baking sheets. Bake at 350 degrees for 9 to 11 minutes. Cool on pans for 3 minutes, and then remove to wire racks.