Step 1Heat the oven to 325 degrees. Oil 4 (4-inch) baking rings and arrange on an oiled baking sheet.
Step 2Place the potatoes in a saucepan and add water to cover by 2 inches. Add about 1 teaspoon salt. Bring to a boil, reduce the heat and simmer until soft but not falling apart.
Step 3While the potatoes cook, combine the vinegar, shallot, thyme and salt to taste in small bowl. Whisk until smooth, then whisk in the olive oil. Season with black pepper to taste. Set aside.
Step 4Drain the potatoes well and let them stand until cool enough to handle, then peel and transfer to a mixing bowl. Cut them into rough chunks. Add half the reserved vinaigrette. Mix with a rubber spatula until well coated. Taste and add more salt if needed and pepper to taste. Divide the mixture among prepared rings, packing to solidify slightly.
Step 5In a second bowl, combine the goat cheese and cream and blend until smooth. Season lavishly with black pepper. Divide among the prepared rings, smoothing the top on each. Bake 15 to 17 minutes, until the cheese is warmed through.
Step 6Transfer the rings to serving plates with a spatula and remove the rings. Arrange olives alongside or around each salad and drizzle vinaigrette around plate. Serve at once.