Step 1

In a large heavy bottomed skillet add the sliced potatoes, broth, water, salt, sugar and 1 Tablespoon of the vinegar to a boil.

Step 2

Reduce heat to simmer, cover and cook until potatoes are tender.

Step 3

Remove the cover and increase the heat to high to reduce the liquid (approx. 2 minutes)

Step 4

Drain the potatoes reserving ½ cup of cooking liquid

Step 5

Add water to make ½ cup if necessary.

Step 6

Whisk in the remaining vinegar, mustard and oil into the cooking liquid

Step 7

Add about ½ cup of the cooked potatoes into the cooking liquid and mash.

Step 8

Pour the thickened sauce over the potatoes and add in the onion, cornichons and chives

Step 9

Season to taste with salt and pepper

Step 10

Serve warm or at room temperature