Preheat oven to 325 degrees and spray an 8x8 pan with non-stick cooking spray. Whisk eggs in a medium bowl using a hand mixer, add oil and coffee and whisk until well blended.
In a separate bowl, combine the brownie mix, espresso powder and white chocolate chips. Slowly add the dry ingredients and blend until combined. Pour batter into the prepared pan and bake for 20 minutes, or until a toothpick inserted into the center comes out clean. Cool completely before cutting.
To make the frosting, in a medium sized bowl combine the butter, yogurt and peppermint extract until smooth. Slowly blend in the dry frosting mix and whisk until smooth. Frost each brownie and top with a sprinkle of crushed peppermint.