use two round cookie cutters (one 6 cm / 2.3'', the other 3.5 cm / 1.4'' diameter) • unsalted butter, well-chilled, diced • powdered sugar • bread flour • cake flour • (2 and 1/2 Tbsp) cocoa powder, sugar-free • Bread flour and cake flour can be replaced with 140g (4.9 oz) all-purpose flour • milk chocolate, couverture • heavy cream, 36% milk fat • bottom cookies, 170℃ / 338 F for 13 minutes • upper cookies, 170℃ / 338 F for 10 minutes • Preheating; 190℃ / 374 F