Put potatoes in a saucepan and cover with cold water. Cover the pan and bring to a boil over high heat. Uncover and boil until the potatoes are tender, between 12 to 15 minutes.
While the potatoes are cooking, make the dressing. In a skillet, saute the bacon over a medium-high heat until most of the fat has been rendered and the bacon is golden and beginning to crisp, about 5 minutes. Turn off the heat and pour off the fat into a glass-measuring cup. Remove the bacon from the pan and let drain on paper towels. In the skillet, with its thin coat of bacon fat, add the garlic and shallots and cook over medium heat, stirring, until softened, about 5 minutes. Add the brown sugar and cook, stirring, until dissolved. Scrape the mixture into a blender or food processor and add the balsamic vinegar, extra-virgin olive oil, and orange juice. Add 1/4 cup of the bacon fat and process, pulsing, until, just until smooth. Season to taste with salt and pepper. Slice the warm potatoes 1/4 inch thick and combine with half of the warm vinaigrette (reheat the vinaigrette in the microwave if necessary) and half of the bacon pieces. Divide in roomy serving bowls. In a large bowl, combine the lettuces, chives, tomato, cucumbers, and celery. Toss with the remaining vinaigrette and divide on top of the potatoes in the serving bowls. Sprinkle the crumbled goat cheese and reserve bacon pieces over the salads, place 3 or 4 croutons on each, and serve.
For the croutons, preheat to 350 degrees. Arrange the bread slices on a baking sheet and brush the tops with garlic oil. Bake 10 to 12 minutes, until golden. Remove from the oven and immediately sprinkle with cheese (if using) and pepper. Cover with foil to keep warm.