For the de-alcoholised Campari:
Using a rotary evaporator distill 1kg of Campari under vacuum at 65 degrees Celsius until all but a thick sugar syrup remains (ie, distill out all of the alcohol and most of the water). There should be approx 100g of Campari syrup remaining per 1L distilled. Rehydrate the syrup by combining 100g Campari Syrup with 100g filtered water.
Maggie Beer’s verjus makes a good substitute for the homemade stuff.
Recipe by Kate McGraw, Isabel, Bondi and makes a 1L batch.