Line a baking sheet with parchment paper or a silicone mat.
In a large bowl, whisk together flour, cocoa powder, baking powder, and salt.
In the bowl of a stand mixer with paddle attachment or in a large bowl with a hand mixer, cream together butter and sugar until light and fluffy, about 2-3 minutes.
Add eggs, one at a time, and mix until combined after each addition. Mix in vanilla extract.
Add the dry ingredients to the wet ingredients and mix until just combined, taking care not to over-mix.
Fold in ¾ cup of the chocolate chunks and ½ cup of the marshmallow fluff, reserving the rest.
Form balls with about 3 tablespoon of cookie dough at a time (I use a #20 cookie scoop) and flatten dough ball in the palm of your hand. Place a caramel candy in the center of the dough and wrap the dough around it, forming a ball. Make sure the caramel is completely covered by the dough.
Place the cookie dough balls on the prepared baking sheets, about 2 inches apart.
Using a toothpick or knife, gently swirl some of the remaining marshmallow fluff into the top of the cookie dough, creating a marbled effect. Add a few more chocolate chunks to the tops of the cookies.
Place cookie sheet in fridge for about 30 minutes to chill and preheat oven to 350 degrees.
Bake chilled cookie dough for 11-13 minutes, until the edges of cookies are just set, but the centers are still soft.
Allow cookies to cool on the baking sheet before moving to metal racks to cool completely.