Preheat your oven to 350°F (175°C). Line a 9x9 inch baking pan with parchment paper, allowing some overhang for easy removal.
In a mixing bowl, melt the butter for the brownie layer. Stir in the granulated sugar, then add the eggs one at a time. Mix in the vanilla extract, cocoa powder, flour, salt, and baking powder until combined. Fold in the chocolate chips.
Pour the brownie batter into the prepared baking pan and spread it evenly. Bake for about 20-25 minutes, or until a toothpick inserted comes out mostly clean. Allow the brownies to cool completely.
In a separate bowl, cream together the softened butter, granulated sugar, and brown sugar until smooth. Mix in the vanilla extract. Gradually add the flour and sweetened condensed milk, mixing until combined. Fold in the mini chocolate chips.
Once the brownies are cooled, scoop out spoonfuls of cookie dough and flatten them into discs. Cut the brownie into 12 squares and place a disc of cookie dough on top of each square. Carefully shape the brownie around the cookie dough to form a ball.
In a double boiler or microwave-safe bowl, melt the semi-sweet chocolate chips with the coconut oil until smooth. If using a microwave, heat in short intervals and stir between each.
Dip each brownie bomb into the melted chocolate, allowing any excess to drip off. Place on a baking sheet lined with parchment paper. Repeat with all brownie bombs.
Refrigerate the brownie bombs for about 30 minutes to allow the chocolate coating to set.