This is such a good thing to do with the abundance of seeds a nasturtium plant throws out. There are lots of variations on the method and I mess around with adding different spices and flavours to each batch, but the basics are, well, pretty basic.
Start by harvesting your seeds, then sprinkle with salt and top up with water to make a brine.
Leave for about 24 hours and then rinse and drain well.
Put in a clean jar and top up with vinegar – this is where you can add other things such as mustard seeds, rosemary, bay, a few chilli flakes… or just leave naked to get the pure peppery taste of the seeds.
Leave a little while for the flavour to develop – the longer the better, but it depends if you want to start using them.
Use in the same way as capers.
I’ve had a jar going strong in the fridge for a couple of years now and they’re still wonderful.