Preheat the oven to 350 degrees F. Line a couple baking sheets with parchment paper or silicone baking mats.

In a large bowl or stand mixer, beat 1 cup butter until is is smooth and creamy, making sure to scrape down the sides and bottom of the bowl.

Add 1 cup sugar and 1/2 cup brown sugar. Cream (this means beat) the mixture for 1-2 minutes on medium speed, stopping to scrape the sides and bottom of the bowl. Once the mixture is light and fluffy, move on to the next step.

Add 1 teaspoon vanilla extract and 2 large eggs. Beat into the butter mixture, scraping the sides and bottom to make sure it's all incorporated.

Add 3 cups of flour (spooned and leveled) but don't mix it in yet.

Add 1 and 1/2 teaspoons baking soda, 1 tablespoon cornstarch, and 3/4 teaspoon kosher salt on top of the flour. Use a small spoon to stir it into the flour. Make sure there are no clumps.

Mix the flour into the dough on low speed. Stop when there are still some streaks of flour. Scrape down the sides of the bowl.

Reserve about 1/4 cup of the Andes mint chips.* We are using them later to top the baked cookies. Chop up 1 cup of dark chocolate (I used Ghirardelli dark chocolate chips). Chop a little extra while you're at it, so that you have some dark chocolate to press into the tops of the baked cookies.

Add the rest of the 10 ounce bag and 1 cup of chopped dark chocolate to the dough. Beat the mixture together, or mix with a wooden spoon if you were using a hand mixer. Do not over beat on this step! You only want to mix until all the chocolate is distributed and all the flour streaks are gone.

Use a cookie scoop or spoon to shape the dough into 1 and 1/2 to 2 inch balls.

Place on the lined baking sheet with about 2 inches in between each cookie.

Bake at 350 degrees F for 10-11 minutes, or until the cookies are set on the edges. Do NOT over bake! The center of the cookie can still have a little bit of shine when you take them out. They will finish cooking on the pan.

Immediately upon taking them out of the oven, use two spoons or the edge of your spatula to push the edges of the cookies toward the center. See this Chewy Chocolate Chip Cookies post for more details. Do this right away, within 60 seconds of taking them out of the oven, before the edges have a time to crisp. This is what makes the center of your cookies ultra chewy and fudgy! It's my favorite cookie tip ever.

When the cookies are still hot, top each one with extra Andes mints and dark chocolate pieces.

Let the cookies finish setting up on the pan for about 5 minutes before transferring to a cooling rack to cool completely. Be sure to eat at least a few when they are warm!

Store these on the counter in a sealed container. They will stay fresh for 2-3 days!