2 cups vanilla pudding (one 5.1 oz package of instant pudding mixed with 1¾ cups milk) or pastry cream
2 bananas, peeled
1 Tablespoon cocoa powder or instant espresso powder
1 cup whipped cream
Pour the milk into a wide, shallow dish. Dip each ladyfinger into the milk to soften them so that they will roll without breaking. (The ladyfingers should be thoroughly soaked, so not to the point of falling apart or becoming soggy.)
Lay a long piece of plastic wrap out on the counter. (It should be large enough to fit two rows of 12 ladyfingers, with a couple of extra inches of plastic wrap on each side.) Place two rows of ladyfingers, side by side, on the plastic wrap . Cover the ladyfingers with a second piece of plastic wrap, and place them in the refrigerator for 4 hours or overnight.
While they are chilling, prepare the whipped cream and the vanilla pudding or pastry cream.
After 4 hours, remove the soaked and chilled ladyfingers from the refrigerator. Check to see if the ladyfingers have softened enough to become rollable. If some of the ladyfingers are still slightly crunchy, use a pastry brush to add a little extra milk to the ladyfingers and return the them to the fridge for an additional hour.
Once the ladyfingers are pliable, take the top layer of plastic wrap off. Spread the pudding or pastry cream in a thin, even layer over the surface of the ladyfingers, leaving a ½-inch border along one of the long sides.
Place the bananas, lengthwise, in the middle of the row of ladyfingers that is completely covered with pudding or pastry cream (the long side without the ½-inch border). You may have to cut one of the bananas so that it fits.
Carefully lifting the bottom piece of plastic wrap on the side with the bananas, roll the ladyfingers up and over the bananas and continue rolling the entire cake to form a cylinder with the ends of the two rows of ladyfingers coming together.
Refrigerate the roll cake, covered in plastic wrap, for at least 30 minutes, or up to 3 hours, to help the cake hold its shape.
Dust a serving tray with cocoa powder or instant espresso powder. Remove the plastic wrap from the roll cak eand place the roll cake on the tray.
Fill a pastry piping bag with whipped cream, or put the whipped cream into a plastic baggy and cut a small hole in one of the bottom corners to make your own pastry bag. Pipe the whipped cream on top of the roll cake to cover the seam between the two rows of ladyfingers.
Dust the top of the roll cake with more cocoa powder or instant espresso powder, and cut the cake roll into slices. (It’s easiest if you cut between the ladyfingers). Serve chilled.