Place 6 eggs in a medium saucepan and cover with cold water.
Add the vinegar and bring to a boil, then remove from the heat, cover and set aside 4 minutes. Meanwhile, fill a bowl with ice water. Using a slotted spoon, remove the eggs and immediately plunge into the ice water to stop the cooking; let sit 2 minutes. Gently peel the eggs and set aside.
Combine the sausage, herbs and one of the remaining eggs in a stand mixer fitted with the paddle attachment.
Mix on medium speed until combined, about 3 minutes. With moistened hands, mold the sausage mixture around the cooked eggs to completely cover.
Preheat the oven to 350 degrees F.
Heat about 3 inches of grapeseed oil in a small high-sided saucepan over medium-high heat until a deep-fry thermometer reads 325 degrees F (or until a pinch of panko sizzles in the oil). Season the flour with 1/2 teaspoon each salt and pepper in a shallow dish. Beat the remaining egg with the milk in another shallow dish.
Put the panko in a third shallow dish.
Roll the sausage-covered eggs in the seasoned flour, shaking off the excess.
Transfer to the egg-milk mixture and turn to completely coat.
Let the excess egg drip off, then roll in the panko.
Fry the eggs until golden brown, about 3 minutes.
Remove to a baking sheet, transfer to the oven and bake until the sausage is cooked through, 10 to 12 minutes.
Mix the mayonnaise, mustard and lemon juice in a small bowl.
