Step 1

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

Step 2

In a large bowl or stand mixer, beat butter until creamy, then add 1 and 1/2 cups sugar. Beat for a couple minutes until light and fluffy, remembering to scrape the sides and bottom of the bowl.

Step 3

Add 2 eggs and vanilla and mix well.

Step 4

Add the cocoa powder and flour, but do not mix yet. Make a well in the flour.

Step 5

Add the cream of tartar, baking soda, baking powder, and salt to the well in the flour, and use a small spoon to blend it in before it hits the wet ingredients. At this point, you can add 1/4 teaspoon cayenne pepper if you like some heat in your cookies!

Step 6

Turn the mixer on low and slowly beat in the flour and cocoa. Mix only until just combined, making sure to scrape the sides and bottom so that it all gets incorporated.

Step 7

At this point you can cover and refrigerate the dough for up to 48 hours if you want, but that is optional. You can bake them right away and they will turn out great.

Step 8

Shape the dough into rounds about 2-3 tablespoons each. Make sure they are uniform.

Step 9

In a shallow bowl, combine 1/4 or 1/3 cup sugar with 1 and 1/2 tablespoons cinnamon. (How much sugar you use is just a matter of preference.) Roll each ball of dough in the cinnamon sugar mixture.

Step 10

Place the sugared dough on the prepared cookie sheets at least 2 inches apart.

Step 11

Bake at 350 for about 10-12 minutes, or until the edges are set and the middle is soft and still shiny. Every oven is different, so keep an eye on it.

Step 12

Let rest on the baking sheet for about 2 minutes.

Step 13

Whenever you can manage it considering how hot they are, use a spatula to transfer each cookie back into the bowl with the cinnamon sugar. (Add more cinnamon/sugar as necessary).

Step 14

Use your fingers to sprinkle the top of the cookie to make sure it's all coated. You need to do this while the cookies are still pretty hot if you want the cinnamon sugar to stick.

Step 15

Transfer the cookies to a wire rack to cool.

Step 16

Eat while still warm! They are so fudgy in the middle and are to-die-for with a glass of milk.