Whisk together oil, vinegar, maple syrup, shallot, mustard, salt and pepper. Toss Brussels sprouts with vinaigrette to coat. (Make-Ahead: Complete recipe to this step; cover and keep chilled up to 1 day.)
Stir in pecans and cranberries just before serving.
Thinly slice Brussels sprouts in food processor with slicer attachment for a quick and easy short cut.