250g/9oz carrots, coarsely grated
1 orange, zest only
1 tsp bicarbonate of soda
200g/7oz light brown sugar
3 tbsp caster sugar
2 tsp mixed spice
¼ tsp fine salt
200g/7oz self-raising flour
100²µ/3½´Ç³ú raisins or sultanas (optional)
200ml/7fl oz vegetable or sunflower oil, plus a little extra for the tin
100²µ/3½´Ç³ú walnut pieces, plus a few extra for decoration
150g/5½oz unsalted butter, softened
250g–300g/9–10½oz full-fat cream cheese, at room temperature
4 free-range eggs, at room temperature