Kohlrabi is a brilliant idea and it will not at all seem much different to the swede in a Branston Pickle type mix which has a wide variety of vegetables in it anyway. Turnip will do at a pinch but you may need to increase the amount of sugar as swedes are generally sweeter. Make sure the chunks are very small. Here is an original recipe which comes out a little dryer than the commercial Cross & Blackwell brand. Some people add tomatoes and more apple in the mix. If you can't find fresh gherkins straight off the vine, buy a cheap commercial jar of them - dice and throw in for good measure. At the end of the day it's finely chopped dates you should want rather than raisins, and flavour comes from the dark brown sugar (Muscovado is best), All spice, standard dark brown malt vinegar, and of course cayenne pepper. Make sure you keep the mix moving, with sufficient liquid. Do not allow the pan to burn at the bottom because the taste will quickly change. If you do catch the bottom of the pan, do not scrape it back into the mix. Decant the content immediately into another pan and leave the burned bottom behind. Also, once the product is in the can, and sealed, do not open and use it for at least a month, to allow the blend to mature (all the flavours will even out naturally over time).
9 ounces carrots, peeled, cut into small chunks
1 medium swede, peeled, cut into small chunks
4-5 garlic cloves, peeled, finely chopped
5 ounces dates, finely chopped
1 small cauliflower, finely chopped
2 onions, peeled and finely chopped
2 medium apples, unpeeled, finely chopped
2 medium courgettes, unpeeled, finely chopped
15-20 small gherkins, finely chopped
10 ounces dark brown sugar
1 teaspoon salt
4 tablespoons lemon juice
3/4 pint malt vinegar
2 teaspoons mustard seeds
2 teaspoons ground allspice
1 teaspoon cayenne pepper