Chocolate sandwich cookies with cream

Ingredients:

• 1.5 cups premium flour + extra for dusting
• 1/4 cup + 1 tbsp cocoa powder
• 0.5 tsp baking powder
• 1/4 teaspoon salt
• 165 g unsalted butter at room temperature
• 2/3 cup granulated sugar + extra for sprinkling
• 1 large egg
• 1 tsp vanilla extract
• 60 g semi-sweet chocolate, chopped
• 1 cup powdered sugar

Preparation:

1. In a bowl, combine flour, 1/4 cup cocoa powder, baking powder, and salt. In a large bowl, beat 110g of butter with granulated sugar using a mixer on medium speed until light and fluffy, about 3-5 minutes. Mix the egg with 0.5 teaspoon of vanilla extract. Reduce mixer speed to medium-low; beat in the flour mixture and knead until smooth.
2. Divide the dough in half and place on 2 pieces of plastic wrap; form into flat rectangles. Wrap the dough in plastic wrap and refrigerate to chill for at least 1 hour.
3. Position oven racks in the upper and lower thirds of the oven; preheat oven to 350°F (175°C). Line 2 baking sheets with parchment paper.
4. Working with one piece at a time, on a lightly floured surface, roll the dough into a 10-inch square (0.3 cm thick). Cut into 1 x 1.5-inch rectangles. Transfer to the prepared baking sheets, prick with a fork, and sprinkle with granulated sugar. Refrigerate the baking sheets until the dough sets, about 15 minutes. Bake, rotating the baking sheets halfway through, until the cookies are set, 13 to 16 minutes. Let cool completely on the baking sheets.
5. Place the chocolate in a microwave-safe bowl; microwave in 30-second intervals, stirring, until smooth; let cool. Add the remaining 55g butter; stir with a silicone spatula until fully incorporated. Stir in the remaining 1 tbsp cocoa powder, the powdered sugar, and the remaining 1/2 tsp vanilla extract. Sandwich the filling between two cookies.