After I wrote about making Sweet Onion Jam last year there has been a lot of interest and people have landed on the blog looking for the recipe all the year around!
Last year I used Rachel Allen's Sweet Onion Jam recipe from her book Bake and it was utterly delicious - possibly the best thing (and most popular among my tasters) I made all year. This year I tweaked the recipe a little bit, mainly to get larger quantities.
The onion jam works best with mature red onions to get the beautiful dark, purpley-red preserve. I did this last year and the jam was a perfect colour. My first batch this year was with brand new onions from the allotment and they hadn't yet fully matured which meant that a lot of the redness boiled away during the cooking process and the jam looked more brown (I assume this is what would happen if you used brown/white/yellow onions too. Using a full bodied red wine also helps with the colour. Rachel adds creme de cassis - I haven't bothered with this either time and haven't missed it.
Last year a few people mentioned that they had made this with the intention of giving it for gifts but the mixture separated so that they had a layer of butter in the jar. Our jam didn't last anywhere near Christmas so I couldn't comment on that. This this year, though, I have made a larger batch so that we have some to keep for later. So far (2 weeks on) there is no buttery layer, however I'm keeping mine at room temperature - not in the fridge.
Sweet Onion Jam
Adapted from Rachel Allen's Bake.
3lbs onions, peeled and sliced finely
275g golden caster sugar
1 tsp sea salt
1 tsp freshly ground black pepper
200ml balsamic vinegar
500ml red wine
Melt the butter in a large pan and add the onions, sugar, salt and pepper. Stir them and cook for 40 minutes over a gentle heat.
Add the vinegar and wine and cook, stirring occasionally, until the mixture is slightly thick (you're looking for a syrupy consistency). The jam will thicken further on cooling.
Place in sterilised jars, seal and label.
The only bad thing about this recipe is the peeling and chopping of 3lbs of onions for what turns out to be quite a small amount of jam. It's still worth it though - think of it as a labour of love!