Scrub the potatoes. In a large saucepan, cook potatoes and the 1 teaspoon kosher salt, covered, in enough boiling water to cover for 8 to 10 minutes or just until tender; drain well. Spread out in a single layer in a shallow baking pan to cool. When cool enough to handle, halve potatoes lengthwise. Set aside.
Wash haricots verts; trim and (if you like) halve crosswise. In a medium saucepan, bring the 3 cups water to boiling. Add haricots verts. Return to boiling. Simmer, uncovered, for 1 to 2 minutes or until just crisp-tender. Immediately remove haricots verts from boiling water with a slotted spoon; plunge into a large bowl half-filled with ice water. Let stand 5 minutes; drain well. Set aside.
In a food processor or blender, combine vinegar, shallot, honey, thyme, mustard, 1/8 teaspoon kosher salt and the pepper. Cover and process or blend until combined. With processor or blender running, slowly add oil in a steady stream until mixture is thickened.
In a large salad bowl, combine potatoes, haricots verts and red onion. Drizzle with enough of the vinaigrette to thoroughly coat. Cover and chill for 2 to 24 hours.
Just before serving, toss salad with bacon and top with feta cheese. Serve with remaining dressing or reserve dressing for another use. Makes 8 to 10 servings.
You will have more dressing than you need, but that's okay. It will keep for a few weeks in the refrigerator and makes a great dressing for another potato salad or pasta salad, or even on a regular green tossed salad.