Preheat oven to 350° F. Line a baking sheet with parchment paper. Set aside.

In the bowl of a stand mixer, combine the butter, granulated sugar, and confectioners' sugar. Mix until just combined.

Drizzle in oil and pour in eggs, water, and vanilla extract. Mix well.

In another bowl, whisk together flour, cocoa, salt, baking soda, and cream of tartar.

Slowly add the flour mixture to the butter mixture and allow the mixer to combine until the dough pulls away from the sides of the mixer bowl.

Using an ice cream/cookie scoop, scoop out golf-ball-size portions on the lined cookie sheet.

Roll out each cookie dough ball until it is smooth and round.

Using a kitchen glass that has been pressed into granulated sugar, press down on each cookie dough ball until the center of the cookie is pressed flatter than the edges. Repeat this on all cookies.

Bake for 7 minutes. Remove from the oven. Note: The cookies will not be completely baked at this point. They will be broiled an additional minute or two after the chocolate and marshmallows are added.

Gently press a piece of chocolate on top of each cookie. Top with half of a marshmallow.

Broil the cookies for another 1-1 1/2 minutes (watching them carefully so they don't get too dark).

Let the cookies cool for 5-10 minutes before serving.