Spray an 8x8 inch square pan with cooking spray, then place a double layer of cling film into the pan and spray with cooking spray.
Place the condensed milk into a deep saucepan and break the chocolate into the pan. Place over a low heat and stir frequently until all the chocolate is melted.
Add in the vanilla, butter and salt and stir until the butter has melted.
Add in the food colouring - add it in gradually, stirring in between additions until you have the desired colour. I used Wilton Gel colour and add in a 1/4tsp at a time. If you use a liquid food colour, you may need the full bottle. Gel is much more concentrated so I would advise using that.
Stir until the fudge is evenly red and then pour into your prepared pan. It should be runny enough to smooth itself out, but you can coax it into an even layer with a spatula.
Sprinkle with sprinkles (ha!) and then leave to cool for an hour before transferring to the fridge to set completely. This took around 4 hours.
When ready to cut, have jug full of warm water and some kitchen paper ready. Lift the fudge out and peel the cling film off. Place on a cutting board and dip a long knife into the warm water, dry it and then cut the fudge into 16-20 squares. I dip the knife every two cuts to keep it as warm as possible, this makes cutting the fudge much easier!
Red Velvet Fudge will keep in an airtight container, in the fridge, for a week.