While the syrup is concentrating, sterilize your jars in boiling water, and then fill them with the fruit. Don't be surprised at how much the fruit has compacted; I started out with 4 1/2 pounds (2 k) of fruit, all of which finally fit into 2 1-pint (500 ml) jars.
After adding the fruit, if you are using mustard oil, pour it in, and then add hot concentrated syrup to cover, tapping the jar repeatedly to dislodge air bubbles as you fill.
If you are instead using powdered mustard, add the infusion and then the hot syrup to cover, tapping jar to dislodge air bubbles as you fill.
Note: If you use all of the infusion the mostarda will be quite strong. I like it that way and did, but feel free to make your first batch a little less strong if you like.


