Beat the butter and sugars together until light and fluffy. Add the egg and vanilla, beat to combine, then stir in the flour and salt, followed by half the chocolate chips and half the fudge chunks. The dough will be very soft, so put it in the fridge for at least 30 minutes to firm up a little.

Spoon the dough onto a piece of baking paper and press into a round, then cover with another piece of baking paper and roll out to about 29cm in diameter. Put the pizza, still on the baking paper, onto a 30cm round pizza tray (the kind with the holes in the bottom) or a large baking sheet. Put in the fridge for another 30 minutes to chill.

Heat the oven to 180C/fan 160C/gas 4. Remove the top sheet of baking paper from the cookie and bake for 10-15 minutes until golden. Remove the cookie from the oven and turn the oven off. Scatter the marshmallows over the cookie, then return it to the turned-off oven for 1 minute, so that the marshmallows melt just a little.

Sprinkle the remaining chocolate chips and fudge chunks over the marshmallows, then use a blowtorch to lightly brown the marshmallows and slightly melt the chocolate and fudge separately. Alternatively, put under a hot grill for 1-2 minutes until lightly charred – taking care as the sugar will burn very easily. Put the salted caramel sauce in a disposable piping or sandwich bag and snip off the end, then drizzle over the top of the cookie. Finish by drizzling with the melted chocolate.