Measure all sauce ingredients into small sauce pan, except cornstarch and water. Bring to boil.
Reduce heat and simmer until duck is done.
After letting salt sit on duck breasts about 15 minutes, rinse salt off and dry thoroughly with paper towel. Season with salt and pepper.
Melt butter and olive oil in cast iron pan. Heat to high.
Add duck breasts to pan. Sear on one side. When color of breast starts to change on the sides, flip breasts and brown the other side. (See step by step photographs in post above.)
USDA recommends cooking cooking duck to 170°F. We like our medium rare, so we cook ours to 135°F. Measure temperature with an instant read meat thermometer.
Set duck breasts on a clean plate. Loosely cover with foil.
To finish sauce, mix cornstarch and water in a small bowl. Add to sauce. Cook about 5 minutes, until thickened and smooth.
Serve duck with sauce.
Notes
Notes** See post for helpful step by step photographs.Do NOT overcook! Duck breasts should be cooked to medium rare, and not over 135°F.Leftovers can be stored up to 3 days in refrigerator.Best if leftovers are eaten cold, such as in salads or sandwiches.