1) Preheat oven to 160 degrees C/Gas 3.
2) Trim fat from oxtails. In a grilling pan, toss oxtails with house seasoning and soy sauce. Top with onions and bay leaves. Add water to fill pan 1/4 of the way to the top. Cover pan with foil and bake until oxtails are tender, about 2 1/2 to 4 hours. Prepare rice according to package directions, adding butter and salt, to taste. Serve rice alongside oxtails.
For the house seasoning:
1) Mix ingredients together and store in an airtight container for up to 6 months.