Preheat the oven to 200C/400F/Gas 6.
For the Vichy carrots, melt the butter in a small frying pan.
Add the brown sugar and heat until it begins to caramelise. Add the orange juice and zest and reduce to a syrup consistency. Add the blanched carrots and mix together.
For the caramelised onions, heat the oil and butter in a small frying pan. Add the onions and cook until soft. Add the brown sugar, and heat until the sugar melts and caramelises. Add the vinegar then stir together.
To serve, place the Vichy carrots onto a warm plate and spoon over the caramelised onions.