Chop the mini chilli very finely and add to the pineapple and rhubarb pieces in the saucepan. Add sugar and vinegar and simmer without a lid. Stir frequently so that nothing hits the bottom.
I pureed the mass after about 10 minutes, then let it boil down until it was quite thick and filled it into prepared screw-top jars.
If you prefer more liquid, just fill up earlier. The amount is sufficient for 3 glasses of 230 ml each.