Ingredients:
1/2 cup unsalted butter (1 stick), melted
1 large egg
1 cup light brown sugar, packed
2 tablespoons brewed coffee, any temperature, optional but recommended (leftover from the morning brew is fine)
1 tablespoon vanilla extract
1/2 teaspoon peppermint extract or mint extract (do not use peppermint oil)
1/2 cup unsweetened natural cocoa powder (Dutch-process may be substituted)
1/2 cup all-purpose flour
25 Mint Oreos, each quartered; divided use (another variety of chocolate sandwich cookies may be substituted such as classic Oreos or storebrand sandwich cookies, noting bars won't taste as minty without using mint cookies)