Pat the duck breast dry and rest it on paper towels to absorb and moisture.
Dry mix together the salt, sugar, prague powder #2, and dried thyme.
While wearing gloves, rub the duck breast with the prague powder mixture.
Place this in a bag and allow it to cure for 2-3 days in the refrigerator.
Remove duck from the bag and wipe off some of the cure. Place the duck breasts in an umai bag. Seal the bag according to the manufacturer’s instructions.
Place the sealed bags on a rack so there is airflow around the entire bag.
Allow the duck to cure in a cool room or a curing box for 2 weeks.
Once the duck is very firm to the touch it can be open and sliced for serving.
Keep the duck prosciutto in a sealed container for up to a month in the refrigerator.