Break the chocolate into pieces and add to a microwave proof bowl. Heat on medium for 1 minute. Remove from the microwave and stir. Repeat heating at shorter intervals, 15 to 20 seconds and stir in between, until the chocolate is completely melted.
Put the condensed milk and cream into a large bowl or a bowl of a stand mixer. Beat with an electric whisk until thick and quite stiff.
Stir in the melted chocolate.
Put the crunchie into a ziplock bag and bash them until broken into uneven pieces.
Add half the crunchie into the ice cream.
Scrape into a lined large loaf tin.
Push the egg into the top of the ice cream.
Cover with cling film and freeze until solid. (I froze mine overnight).