Combine all ingredients in a mason jar: extra virgin olive oil, apple cider vinegar, maple syrup, Dijon mustard, Kosher salt, and freshly ground black pepper. Seal tightly with a lid, then shake vigorously to emulsify. Taste.
Pour enough light, neutral oil into a deep, heavy bottomed pot. Heat over medium-high heat until it reaches 375F.
Heat a skillet over medium-high heat. To the dry pan, add cubed pancetta. Cook, stirring occasionally, until the fat has rendered. Use a slotted spoon to transfer the pancetta to a paper towel lined wire rack.
Once the oil comes up to temperature, carefully lower in the Brussels sprouts. I like to use a spider to do this without splashing hot oil. Cook until golden brown and crispy. Use a spider or slotted spoon to transfer the crispy Brussels sprouts.
Place the drained Brussels sprouts in a large bowl along with crispy pancetta, shaved Parmesan, and pistachios. Drizzle as much of the vinaigrette on as you like, then toss well to thoroughly combine. Transfer to a serve plate or bowl.