Ingredients

• 4 ounces of bittersweet chocolate, chopped
• 3 sticks butter, room temperature
• 1 cup flour
• ½ cup cocoa powder
• ½ teaspoon baking powder
• ½ cup light brown sugar
• ½ cup granulated sugar
• 1 teaspoon vanilla extract
• ¼ teaspoon salt
• 2 eggs, at room temperature
• ¼ cup plain yogurt
• 3 cups confectioner’s sugar

Directions

• Preheat the oven to 375 degrees F and line 2 baking sheets with parchment paper.
• Melt the chocolate and 1 stick of butter over medium heat in a double boiler. Remove from heat and set aside to cool slightly.
• In a medium bowl, whisk together the flour, cocoa powder, and baking powder. Ser aside.
• To the bowl with the melted chocolate, add the brown sugar, granulated sugar, vanilla, and salt. Whisk to combine. Whisk in the eggs, one at a time, followed by the yogurt. Using a rubber spatula, fold in the flour mixture being careful to avoid overmixing.
• Scoop 1-tablespoon mounds of the batter on the prepared baking sheets, leaving about 1 inch between each cookie. Bake the cookies for about 9 minutes. Slide the cookies onto the parchment onto a cooling rack and cool completely. 
• Meanwhile, make the filling. In a medium bowl, using an electric hand mixer, beat the remaining two sticks of butter and the confectioner’s sugar; mix until light and fluffy, starting on low speed to avoid splatter and work up to medium speed. Add the vanilla extract and salt and beat on medium speed.
• Spread the filling on the flat side of half of the cookies. Top with the remaining cookies. Store in an airtight container until ready to serve.