For the salad: Place the bacon lardons into a saute pan and cook to render the fat and crisp. Remove the bacon lardons and reserve 1/2 cup bacon fat for the dressing. Drain the frisee and fennel and dry in a salad spinner. Set the frisee and fennel aside in a medium bowl.
To the same bowl add the reserved bacon, pickled onions, and warm vinaigrette dressing that has been spooned around the side of the bowl. Spooning the dressing on the side of the bowl helps from overdressing the salad itself. Toss to combine.
For the poached egg: Add 2 cups or about 1-inch white wine to a saucepan and add a splash of vinegar and big pinch salt. Add the bouquet garni to the saucepan and bring the mixture to a slow simmer. Once at a slow simmer, remove the bouquet garni. Carefully crack the egg into a ramekin. Gently slide the cracked egg into the liquid and poach. While the egg is cooking, baste or spoon some of the hot liquid over the egg to cook evenly, about 45 seconds to 1 minute. Remove the egg from the liquid with a slotted spoon and place into a small dish. Season the egg with sea salt and freshly ground black pepper.
For serving: Place the toast slice onto a plate. Top with the salad and egg. Garnish with more bacon, sea salt, freshly ground black pepper, extra-virgin olive oil. Drizzle with more dressing and garnish with fresh tarragon, if desired.
For the vinaigrette: Combine the shallot, garlic, salt, vinegar, mustard, and salt in a medium mixing bowl. Whisk in a few drops of the bacon fat and then begin adding the bacon fat in a thin stream, whisking continuously until all the oil is incorporated. Taste the dressing and season with salt and freshly ground black pepper.
For the pickled onions: Pack the onions in 2 (1-quart) jars and cover the water to come within 1/2-inch of the rim. Pour the water out into a measuring cup. Note the volume, pour off half of the water and replace it with vinegar. Add 2 tablespoons sugar and 2 tablespoons salt for every 3 cups of liquid. Pour the vinegar mixture into a nonreactive saucepan, add the garlic, bay leaves, coriander seeds, black peppercorns, red pepper flakes, and mustard seeds, and bring to a boil over high heat. Allow the liquid to boil for 2 minutes, and then remove it from the heat.
Pour the hot liquid into the jars to cover the onions and screw on the lids. Refrigerate for up to 1 month.