Chocolate Chunk Coffee Muffins

Ingredients (15)

• 4 tablespoons unsalted butter
• 4 ounces bittersweet chocolate
• 2 cups all-purpose flour
• 1/2 cup  granulated sugar
• 1/3 cup unsweetened cocoa powder
• 1 tablespoon baking powder
• 1 tablespoon espresso powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon ground cinnamon
• 1/2 teaspoon kosher salt
• 1/3 cup light brown sugar
• 1 cup strong coffee
• 1/4 cup non-fat plain Greek yogurt
• 1 large egg
• 1 teaspoon pure vanilla extract