Select a large mug (a smaller one will result in an overflowing cake).
Put your mug onto a microwave safe plate (just in case it does overflow!).
Place butter into your mug and microwave for 10 seconds (or until melted).
Add the egg, milk and vanilla essence and lightly beat with a fork until combined.
Add the dry ingredients into your mug and beat with a fork until well combined (no lumps!).
Place mug into the microwave and cook for 30 seconds on medium heat.
Place the caramel chocolate squares into the middle of the cake.
Place the mug back into the microwave for a further 30 seconds on medium heat (watch it carefully to make sure it doesn't overflow).
The cake should be cooked on the outside and gooey in the middle.
If you think it's still a little undercooked (all microwaves are different), then pop it back into the microwave and cook for a further 10 seconds on medium.
Repeat until it's cooked how you like (don't overcook it though or else it will be dry and yuck... keep it gooey and moist - like a pudding!!).
Take out of the microwave and top with your choice of extras - I used salted caramel ice-cream and chocolate sauce.
You could also use chopped nuts, whipped cream, chocolate bits, strawberries or berry coulis.