Heat oven to 325°. Place paper liners in cups of mini muffin pans (36 total).
In a small bowl, whisk together flour, cocoa, baking powder, baking soda and salt.
In a large bowl, beat together butter and sugar. Beat in eggs, one at a time, beating well after each addition. Beat in yogurt. On low, beat in half the flour mixture. Pour in 2/3 cup water and beat on low until blended. Scrape down side of bowl. On low, beat in remaining flour mixture.
Divide batter among prepared cups. Bake at 325° for 19 minutes. Cool completely. Frost and decorate as desired.
