Preheat your grill to 450°F. Place the peppers and onion over direct heat to grill.
Heat 2 tsp. peanut oil in a sauce pan and sauté the garlic and ginger until fregrant, being careful not to burn the garlic. Add the soy sauce, water, and brown sugar, bringing the pot to a simmer.
Check and flip the peppers and onions, making sure they get an even grilling on all sides. If you find they're getting too dark, move them to indirect heat to finish cooking.
Season the beef with the Bone Dust and Five Spice then thread the sliced beef onto the skewers. You can put two to three slices per skewer.
Remove the sauce from the heat if it has thickened, if you would like it thicker, place it on the heat and add the cornstarch mixture, stirring for another minute or two until thickened. Then remove from heat.
Set the peppers and onion on a plate to cool enough to slice while you grill the beef. Brush the beef skewers with the remaining oil and grill over direct heat for 2 to 5 minutes per side.
Serve the beef over the sliced peppers and onions, with rice and pour the sauce over top (generously, 'cause it's good). Top with sliced green onion.