Peppermint Mocha Thumbprints

Ingredients

• 1 large egg
• ¼ teaspoon salt
• ½ teaspoon baking soda
• ½ cup unsweetened cocoa powder
• ½ cup heavy cream
• 1½ cups all-purpose flour
• 1 teaspoon pure vanilla extract
• ½ cup packed light brown sugar
• 2 teaspoons milk
• 1 tablespoon espresso powder
• ½ cup (1 stick) butter, softened
• ⅓ cup sugar + additional sugar for rolling
• Crushed candy canes for topping
• 4 ounce semi-sweet chocolate bar, finely chopped (or ½ cup semi-sweet chocolate chips)
• ⅛ – ¼ teaspoon peppermint extract