4 large baking potatoes (idaho or russet)
1/4 cup olive oil
Kosher salt
1/4 cup sliced scallions
1/4 cup chopped mixed fresh herbs, such as chives, drill and parsley
1 1/2 cups sour cream (or plain Greek yogurt)
Freshly ground pepper
1/2 stick (1/4 cup) unsalted butter, at room temperature