Notes: You can prepare the potatoes (steps 1 and 2) up to 2 hours before serving; cover loosely and let stand at room temperature, stirring occasionally. You can cook the sausage (step 3) up to 1 day ahead; cover sausage and cooking liquid separately and chill. Heat liquid in pan before adding to potatoes in step 5.
2 pounds thin-skinned potatoes (1 1/2 in. wide), scrubbed
1/3 cup extra-virgin olive oil
2 tablespoons red wine vinegar
2 tablespoons dry white wine or 1 more tablespoon red wine vinegar
1/4 cup minced shallots
About 1 teaspoon salt
3/4 teaspoon white pepper
2 pounds mild Italian sausages
Fat-skimmed chicken broth (optional)
1 tablespoon Dijon mustard
1/3 cup chopped parsley
2 tablespoons thinly sliced fresh chives or green onions
1 tablespoon minced fresh tarragon or oregano leaves
6 ounces arugula leaves (2 qt.), rinsed and crisped
How to Make It
Combine potatoes and 1 to 1 1/2 quarts water in a 5- to 6-quart pan; bring to a boil over high heat, then cover, reduce heat, and simmer just until potatoes are tender when pierced, 15 to 20 minutes. Drain and return to pan. Shake gently over medium heat until liquid is evaporated, about 2 minutes. Remove from heat.
Meanwhile, combine sausages and 1/3 cup water in a 10- to 12-inch frying pan over medium heat; cover and cook until sausages are firm to touch, about 10 minutes. Pour cooking liquid into a 1-cup glass measure; skim off fat and discard. You need 1/4 cup liquid; add chicken broth if necessary or discard remaining. Whisk mustard into measured liquid until smooth.
Turn sausages occasionally in pan over medium-high heat until browned, 5 to 7 minutes. Transfer to a board and slice diagonally about 1/4 inch thick.
Add sausages, warm cooking liquid, parsley, chives, and tarragon to potatoes; mix gently. Add salt to taste. Add arugula and mix gently. Pour into a large bowl. Serve warm.