First, peel the bananas, cut them into coins and freeze them in a single layer on a plate for 1 to 2 hours. If they have been in the freezer longer, let them sit out for 15 minutes before blending.

Next, beat the shortening, peanut butter, egg, both sugars and the vanilla until smooth, then stir in the fine salt, flour, baking soda and baking powder. Cover and refrigerate for at least 3 hours.

Then heat the oven to 375F. Roll the chilled dough into balls a little larger than 1 inch, set them on ungreased baking sheets and flatten each one in a crosshatch pattern with a fork dipped in flour.

Bake for 10 to 12 minutes, pulling them while the centers still look slightly underdone, then cool completely on a rack. A warm cookie will melt the filling on contact.

After that, blitz the frozen banana in a food processor, scraping the sides down every 30 seconds. It will look like rubble, then ball up and seem ruined, then break smooth and creamy after 3 to 5 minutes. Pulse in the toasted coconut and the pinch of salt.

Lay half the cookies face down on a lined sheet, add a generous spoonful of the banana base to each, cap with a second cookie and press until the filling reaches the edge. Freeze the tray for about 30 minutes.

Meanwhile, microwave half the chocolate chips in 30 second bursts until melted, then stir in the rest off the heat until smooth and add the espresso powder. Transfer to a plastic bag and snip a tiny corner.

Finally, drizzle three or four at a time and sprinkle each batch with flaky salt straight away, before the chocolate sets. Freeze for another 30 minutes, then wrap each one individually for storage.