It's not surprising when you start to add up all of the calories in all of the dishes, mains and sides, that people in the UK and other Western countries take in by eating Christmas lunch alone we are talking at a massive amount of caloric intake, for just one meal, not to mention the whole day through . . .  as the feasting begins in the morning and continues on up into the night!   I have tried to come up with a few sides this year that won't break the calorie bank, and yet are still delicious and which feel luxurious.  This Skinny Sprout and Carrot Gratin I am showing you today is one of them.