My wife makes a chilli paste and freezes it in thin layers in sandwich bags. That way it keeps for yonks, you just open the bag, slide the chilli out, cut a bit off using scissors or a knife (you can break some off with your fingers but have to remember to wash your hands well after…) and chuck it in whatever you’re cooking. It really retains the flavour as well as the heat of the chillies.
From memory, you put a big handful of chillies in the blender with a couple of peeled garlic cloves and a spoonful of cider vinegar.
Then, and this is really important, take the blender outside, and plug it in using an extension cord.
Whizz it up until there are no big bits left, pour into sandwich bags, seal them with as little air in as possible, and lay flat in the freezer. The layer of chilli paste should be around 3-4 mm thick.
If you try to blend it in the house, your house will fill with capsaicin vapour and you will have to leave quickly, and in pain. You will not be able to re-enter the house for quite some time – or you can, but you need to have your eyes closed and be holding your breath while you fumble your way round opening windows… if you left the blender running when you ran screaming from the house, then you’re stuffed.