Mix: In a medium mixing bowl, whisk together the milk, condensed milk, and instant vanilla pudding mix until thoroughly combined. Cover and chill in the fridge for at least 1 hour until it thickens firms up into a pudding consistency.
Whip cream: In a large mixing bowl, add the whipping cream. Use a whisk or an electric hand mixer to beat the cream until it becomes firm peaks.
Fold together: Add the pudding to the whipped cream and fold together with a spatula until no streaks remain. Set aside.
Espresso Soak
Mix: In a shallow bowl, stir together espresso powder, hot water, and coffee liqueur until the espresso powder has dissolved.
Assemble
Dip ladyfingers: Briefly dip a ladyfinger into the espresso soak for only about 1 second on each side. Do NOT let the ladyfingers sit in the soak for too long otherwise it will quickly turn into mush. Let some of the excess drip off before placing it in the bottom of a large casserole dish. Repeat with half of the ladyfingers until you've arranged a whole layer on the bottom of the dish.
Layer: Add about ¼ of the pudding on top of the ladyfinger layer. Use an offset spatula to smooth it into an even layer. Scatter half of the banana slices across the pudding layer. Spread another ¼ of the pudding on top of the banana slices. Repeat with the rest of the ladyfingers, banana slices, and pudding.
Chill: Cover and chill in the fridge for at least 4 hours or overnight.
Dust: Before serving, use a fine mesh sieve to dust the top with cocoa powder.