Preheat the Oven: Set your oven to 350°F (175°C) and grease a baking sheet.

Mix Dry Ingredients: In a bowl, mix together the flour, cocoa powder, baking powder, and salt until well combined.

Cream Butter and Sugar: In another bowl, cream the softened butter and granulated sugar together until fluffy, about 2-3 minutes.

Add Eggs and Vanilla: Beat in the eggs one at a time, ensuring they are fully incorporated before adding the next. Then, blend in the vanilla extract.

Combine Mixtures: Gradually add the dry mixture to the wet ingredients, mixing until just combined.

Drop Dough onto Baking Sheet: Use a spoon or cookie scoop to drop spoonfuls of dough onto the prepared baking sheet, leaving space between each cookie.

Bake the Cookies: Place the baking sheet in the oven and bake for 12-15 minutes or until cookies are set but still soft.

Make the Custard: While the cookies cool, whisk together the heavy cream and powdered sugar in a bowl until thick. Add the vanilla extract for flavor.

Construct the Sandwiches: Once the cookies are completely cool, spread a generous amount of custard on the bottom side of one cookie and place another cookie on top.

Add the Chocolate Drizzle: Melt the milk chocolate chips and drizzle over the top of each cookie sandwich.

Let Set: Allow the chocolate to cool and set before serving.