In a small mixing bowl, whisk the creme fraiche, mustard, vinegar and honey. Season with salt and pepper and set aside.
Fill a large deep skillet with 2 to 3 inches canola oil; heat to 350 degrees F over medium-high heat. Add half of the Brussels sprouts in small batches, waiting for the bubbling to subside before adding more; they should begin to sizzle and fry immediately. Cook, stirring occasionally, until crispy and golden, 5 to 7 minutes. Remove the Brussels sprouts with a slotted spoon and place on a cooling rack set over a baking sheet. Season generously with salt. Repeat with the remaining Brussels sprouts.
Put the Brussels sprouts on a platter and drizzle with half of the dressing; toss. Season with salt and pepper and top with the apple. Serve with the remaining dressing.