Line a 8" square tin with greaseproof paper. I grease the tin first with a little butter to help the paper stick to it
Put the condensed milk, dark chocolate and milk chocolate in a pan and melt together on a low heat, stirring together as it melts
Once it's fully melted and combined, take the pan off the heat and stir in the icing sugar
Put half of the mixture into the tin, smooth it down, and press some of the Terry's Chocolate Orange pieces into it
Put the rest of the fudge mixture over the top, and smooth down
Melt the white chocolate and colour it bright orange with the food colouring. Add blobs to the top of the fudge and use a cocktail stick to swirl it around
Then add the rest of the Terry's Chocolate Orange pieces on top, breaking them in half if needed and pressing them in
Add some sprinkles if you like, then put in the fridge overnight, or for 3-4 hours to set
Remove from the tin and slice into pieces to serve. Store in the fridge for 2-3 weeks