Rinse and scrub potatoes; cut into bite-size pieces. Put potatoes in a large pot, cover with cold water, and bring to a boil. Add 1 tbsp. salt, adjust heat to maintain a slow boil, and cook potatoes until tender to the bite, about 8 minutes.
Drain potatoes and put in a large bowl. Toss with 3 tbsp. lemon juice and let sit until cooled to room temperature, 20 to 30 minutes.
Meanwhile, chop chives (you want about 1/2 cup) and dill (you want about 2 tbsp.).
Put cream in a medium bowl and beat until soft peaks form. Beat in white pepper, remaining 1 tsp. salt, and remaining 1 tsp. lemon juice. Stir in chives and dill. Gently toss cooled potatoes with dressing. Serve immediately.
Note: Nutritional analysis is per serving.