In a medium saucepan, melt the

butter and chocolate chips, stirring frequently, over medium heat. Remove from heat and let cool.

In a medium bowl, whisk

together the flour, cocoa powder, baking powder and salt.

Using an electric mixer, beat

the sugar, eggs and vanilla at low speed until smooth, 2 minutes. Mix in

the cooled chocolate mixture just until blended. Add the flour mixture, mixing on low speed until just combined.

Cover and refrigerate the dough

for an hour.

Preheat oven to 325 degrees. Using a lined baking sheet, scoop about a tablespoon of the dough

and roll between your palms to form 1-inch balls. Arrange about 16 balls 2

inches apart on each cookie sheet.

Bake in the center of the oven, until the

tops of the cookies crack, about 12 minutes.

Meanwhile, snip 8 marshmallows

in half crosswise and press 1 square of chocolate onto each of the cut

sides.

Remove the cookie sheet from

the oven; gently press a marshmallow half, chocolate side down, into each

cookie. Bake, on the top rack, until the marshmallows are just softened, about 4 minutes. *Store the remaining cookie dough in the fridge while you

are baking to keep it cool.

Let cookies cool for 5 minutes;

grate the remaining chocolate over the hot cookies. Using a spatula,

transfer the cookies to cooling rack; let cool slightly.

Repeat the process with

the remaining dough, marshmallows and chocolate.