To make dressing, combine Dijon mustard, garlic, shallots, thyme leaves, bacon (with drippings) and hazelnuts in a blender. Blend on medium speed, adding hazelnut oil, vinegar, maple syrup and water. Add salt and a few grinds of fresh peppercorns to taste.
In a large saucepan that will accommodate all the kale, sauté the lardoons until nicely browned. Add shallots and shredded Brussels sprouts and continue to sauté until the sprouts begin to soften. Add the dressing and kale. Work all the ingredients together over the heat until the kale begins to wilt. Remove from pan and plate the salad. Top with toasted chopped hazelnuts.