In a large saute pan, render the bacon until crispy. Add the shallot and garlic and cook until softened and translucent. Remove from the heat and whisk in the mustard, 3 tablespoons of the vinegar, and the brown sugar. While continuing to whisk, add the canola oil in a thin, steady stream. Season lightly with salt and remove all but 1/3 cup of the vinaigrette from the saute pan. (Remaining Bacon Vinaigrette may be refrigerated up to 1 week and used as desired.)

Preheat a deep fryer to 350 degrees F.

Fry the Brussels sprouts (in two batches) until golden and crispy around the edges, 1 to 2 minutes. Transfer to paper towels to drain. (Note:  Be careful -- the Brussels sprouts will splatter when you add them to the hot oil!) Repeat with the remaining sprouts.

To serve, toss the crispy Brussels sprouts in the saute pan with the warm Bacon Vinaigrette, along with the remaining tablespoon of sherry vinegar and the butter. Season to taste with salt and serve warm, garnished with the parsley.