Place a double layer of cling film into an 8x8 inch square pan, with 3-4 inches of over hang and spray with cooking spray. I used Wilton Bake Easy. It's important to have two layers of cling film, so it's strong enough to lift the fudge out without breaking. (See note)

Place Eggnog and sugar into a large, non-stick if possible, pan and place over a medium heat.

Bring to a boil and then start stirring continuously for 10 minutes until the Eggnog mixture gets thick. You will notice that most of the moisture evaporates and it coats the back of your spoon. If you use a non-stick pan, as you stir it will completely come away from the pan as you stir it. It will take around 10 minutes to get to this stage.

Remove from the heat and add in the Marshmallow Fluff and butter. Stir until both are melted and well incorporated.

Add in the white chocolate one handful at a time, stirring until melted. Once the mixture is smooth and well combined, add in the vanilla, rum extract (if using), nutmeg, cinnamon and salt and stir until combined.

Tip the fudge mixture into your prepared pan and smooth into a level layer with the back of a spoon/spatula. Leave to cool for 30 mins-1 hour and then cover loosely with cling film before placing into the fridge to cool and set completely.

Once set, wiggle each side of the cling film until it loosens, then transfer to a cutting board.

I find it easiest to slce the fudge with a hot knife. I keep dipping the knife into hot water and wiping it dry before making 2-3 slices with it.

Slice into 16-24 pieces of fudge and transfer to an airtight container. Fudge will keep in the fridge for 10 days, or at room temperature for a week.

To serve, leave out of the fridge for at least 15 minutes. You can also sprinkle with more nutmeg.