Creamy Cocoa Cookies with Fat Fudge Frosting

I found these cute little cookie sandwiches at Conversations with a Cupcake . Go check out her cutie patootie food photos on her blog. For the record, even though I made more than 200 cookies, so 100+ sandwiches, I only taste-tested one since it was the first time I made them. But I was tempted. They are very good. I made them for the girls at girls camp and I was told they were gone in 30 seconds---all 100+ sandwiches. I made mine small and I got around 54 cookies each batch.

Creamy Cocoa Cookies with Fat Fudge Frosting
3/4 c. butter
1 1/4 c. brown sugar
2 eggs
1 t. vanilla

1/4 t. cream of tartar
2/3 c. cocoa powder
1/2 t. salt
1/2 t. baking powder
1 3/4 c. flour

Spray cookie sheets. Preheat to 400°. Cream together butter, sugar, eggs, and vanilla. Mix remaining ingredients in a separate bowl and add a little at a time to the creamed mixture. (Dough is very thick.) Refrigerate dough for about an hour. Roll into balls, and bake for 7-9 minutes, or just until outside is cooked. Do not overbake. Allow to cool completely on a rack. Use frosting recipe below to frost or to create cookie sandwiches.

Fat Fudge Frosting
2/3 c. butter, melted
1/3 c. cocoa powder
4 c. powdered sugar
1/2 t. vanilla
2-4 T. milk
Sprinkles

Combine first four ingredients in a large bowl. Add milk slowly, by tablespoons until frosting is creamy looking. Allow to cool and thicken before spreading on cooled cookies, then rolling in sprinkles.