Line a 1 litre capacity bowl with two layers of plastic wrap, making sure the wrap overhangs the top of the bowl. I used an actual steamed pudding bowl, but any bowl of similar size will work.
Put the condensed milk and butter into a large heatproof bowl and microwave on high for 1 minute. Stir, then continue to heat in 30 second bursts, stirring in between, just until the butter is completely melted and combined.
Add the dark chocolate and leave it to sit and melt for a minute or two. Give it a stir and if the chocolate isn’t melted, heat on 50% power in 30 second bursts, stirring in between, until the chocolate is melted.
Add the smaller amount of peppermint extract and give it a taste, adding more if necessary. Peppermint extracts vary in strength, so make sure you taste it as you add.
Leave to cool slightly - we don’t want to melt the chocolate chips when we add them. Pop it in the fridge for a few minutes if you’re in a hurry.
While the mixture cools, crush the biscuits/cookies. I just crush them with my hands so the chunks are uneven. If you’re using quite firm/hard cookies then it’s better to break them into smaller pieces, as it will make the pudding easier to cut.
Add the biscuits and chocolate chips to the cooled chocolate mixture and stir until well combined.
Press the mixture into the lined pudding bowl. Refrigerate for at least 4-6 hours. Overnight is ideal.
Remove the pudding from the bowl and turn onto a serving plate.
In a heatproof jug or bowl, melt the white chocolate and oil in the microwave on 50% power in short bursts, stirring in between, until fully melted. Spoon onto the top of the pudding, allowing it to drip down the sides.
Store, covered, in the refrigerator until ready to serve. Top with crushed candy canes if desired, right before serving.
Notes
The pudding should stay firm outside of the fridge for half an hour or so, depending on room temperature. If you need it to stay out for longer before serving, you can increase the amount of dark chocolate to 300g.Pudding bowl - If you don't have a steamed pudding bowl or other 1-litre (approx 2 US pint) capacity bowl, you can press the mixture into a baking paper-lined small loaf pan, or small round or square cake pan instead. *Biscuits- You can use any plain or flavoured biscuits/cookies that you like in this recipe. I made this gluten-free with Arnotts Rice Cookies.Mix-ins - You can also use whatever extra mix-ins that you like in place of the white and milk chocolate chips.Candy canes - Add the crushed candy canes to the top of the pudding close to serving, as they can start to dissolve in the fridge.