Preheat oven to 450°F.
Coat rimmed baking sheet with nonstick spray or line with a piece of parchment paper.
Rinse brussel sprouts, discard leaves that are brown.
Slice brussel sprouts in half and place on prepared tray in a pile.
Whisk together olive oil, mustard, and honey.
Pour half of the mixture over brussels sprouts, and toss to coat fully.
Spread brussel sprouts in a single layer, leaving a small corner of the tray empty, if possible.
Season with salt and pepper, if desired.
Bake for 20 minutes.
Place capers in the empty corner of the tray; bake for an additional 10 minutes.
Transfer brussel sprouts to a serving bowl, and top with remaining mustard mixture; toss well.
Sprinkle with crispy capers.