Place duck eggs in a pot and cover with cold water by 1 inch (12 eggs)
Bring to a boil over high heat
Once boiling, cover, remove from heat and let sit 12 minutes
Transfer to an ice bath for 10 minutes
Peel eggs carefully (under running water if needed)
Slice eggs in half lengthwise and scoop yolks into a bowl
Mash yolks with a fork, then add mayo, mustard, vinegar, salt and pepper, mixing until smooth and creamy (egg yolks, 1/2 cup mayo, 1 tbsp mustard, salt and pepper to taste)