Coat your pork pieces in cornstarch. Heat up the oil in a large skillet over medium-high heat. Brown the pork quickly in the pan.  We are not looking to cook the pork through, just get a little color on each side. Place the browned pork in the slow cooker. Add the chopped bell peppers, onion, and pineapple (reserve the juice).

In a small mixing bowl combine the sugar, brown sugar, pineapple juice, vinegar, soy, ketchup, garlic, ginger, and pepper. Pour the sauce over the pork in the slow cooker and stir. Cook on low for 4 hours, stirring once or twice to make sure the sugars are not burning. Garnish with scallions and sesame seeds and serve over white rice