1. Stir mustard, honey and oil in a large bowl until smooth. Add pork cubes and toss to coat. Set aside at room temperature. Soak 8 bamboo skewers in cold water for 20 minutes.
2. Preheat broiler to high and line a broiling pan with foil. (Alternatively, light a charcoal fire and let it burn to gray ash.) Divide pork and peppers into 8 portions and skewer cubes, alternating with squares of pepper (begin and end with pepper; use about 6 pepper pieces and 5 pork chunks per skewer). Thread each skewer as close as possible to center of pieces, to facilitate turning. Season with salt and pepper.
3. Broil or grill 6 to 8 inches from heat source, turning often, until slightly browned and pork is cooked through, 12 to 15 minutes.