Step 1

Preheat oven to 350°F. Place potatoes in a small bowl, and drizzle with oil. Sprinkle with 1 teaspoon of the salt; toss to coat. Spread potatoes in a single layer on a baking sheet, and bake until tender when pierced, about 40 minutes. Remove from oven, and cool 15 minutes.

Step 2

Cut each potato in half crosswise. Carefully scoop out potato pulp into a medium bowl, leaving shells intact. Place shells, cut side up, on baking sheet, and bake in preheated oven until dry, about 10 more minutes. Cool completely, about 30 minutes.

Step 3

Stir together potato pulp, sour cream, capers, parsley, dill, mustard, zest, and remaining 1/2 teaspoon salt. Spoon mixture generously into each potato shell.