Preheat oven to 350F.
Position oven rack in the middle of the oven.
Place parchment paper in a 9X9 inch pan so it covers the bottom and 2 sides (to facilitate the brownie/fudge removal).
Butter the pan or spray it with baking spray and set aside.
Add 10 ounces of chocolate melts or chopped chocolate to a microwave safe bowl and microwave for 25-30 seconds, stir using a rubber spatula and microwave again for 25-30 seconds. Stir well, and if needed microwave again for a few seconds, careful not to burn the chocolate.
Stir well melted chocolate until smooth and set aside.
In a mixing bowl, cream butter and sugar until the mixture is light, pale and fluffy. Stop once to scrape the sides and bottom of the bowl.
Add the eggs one at a time and whisk well on low-medium speed after each addition. Add mint extract and mix again for about 5 minutes on medium-high speed.
In a small bowl or cup, mix together the espresso powder with warm water until the espresso powder has fully dissolved.
Add the espresso mixture and melted chocolate to the batter and mix on low-medium speed until just combined. Stop once to scrape the sides and bottom of the bowl.
In a separate bowl, whisk together flour and cocoa powder and add the mixture to the batter. Mix on low speed until just combined, or fold it in with a spatula.
Using a spatula, fold in ½ cup of mini chocolate chips.
Pour the batter into the prepared pan, use a spatula to spread the batter evenly over the entire pan.
Bake for 35-40 minutes or until an inserted toothpick comes out covered in a few sticky crumbs. I baked my brownies for 35 minutes.
Let the brownie cool down to room temperature before adding the mint chocolate chip fudge layer.
If the brownie layer is not very flat use a spatula to level it by pressing down the sides of the brownie.