Homemade Milano cookies, plain and mint (langue de chat cookies sandwiched with tempered chocolate)

Preheat the oven to 350F for the test bake.

Work the butter with a spatula until homogeneous; sift in the powdered sugar and work until creamy and fully incorporated, then whisk to lighten.

Add the vanilla, then whisk in the egg whites well.

Mix the flour, baking powder and salt in a separate bowl, add, and work until there are no lumps.

Fill a piping bag with a round tip of about one centimeter; pipe lines about 5 to 5.5 cm long on marked parchment on a sheet tray.

Test bake at 350F on the bottom rack, checking at 7 minutes; the edges browned too dark and the inside was cakey.

Dry the baked cookies in a countertop convection oven at no higher than 200, 20 minutes, so they crisp through without browning.

Insulate by doubling the baking sheets with a small air gap between them to stop browning on the bottom.

Make the final batter with cake flour and pipe onto a Silpat on doubled baking sheets.

Bake at 325F for 6 minutes; while still soft, push the edges straight to shape, let cool slightly and dab on a small tail of batter with a finger.

Return to the 325F oven, checking closely, until a pale golden brown ring forms at the edge.

Cool, then dry flat in the drying oven until firm with a snap; pair the cookies by size.

Whisk confectioners sugar with milk dribbled in, a little vanilla extract, peppermint extract drop by drop and a pinch of salt to a thick glaze.

Spread a thin layer of glaze to the very edge of one cookie from some pairs, scrape off the excess, and leave exposed to the air to set.

Chop 140 g chocolate finely and set aside 35 g as seed.

Melt the chocolate over a water bath on an induction cooktop to 116F; add the seed chocolate, drop the water to 90F with ice and stir until the seed melts and the chocolate is at 90F; test a stripe on an offset spatula.

Pipe chocolate onto one cookie, with more at each end because the cookies are not flat, and sandwich with its pair.