Cook 1 cup of short-grain rice according to package instructions, about 15-20 minutes. Let cool slightly.

Heat 1 tablespoon of oil in a skillet over medium heat. Stir-fry chopped onions until translucent, about 3-4 minutes. Add selected vegetables and cook until tender. Combine cooled rice with 2 tablespoons of demi-glace or stock and a splash of soy sauce. Stir until heated through, about 4-5 minutes.

Whisk together 3 large eggs in a separate bowl. Heat a non-stick frying pan, coat it with cooking spray. Pour in the egg mixture, swirling to coat the pan. Cook for 2-3 minutes, until edges are set but center is runny.

Spoon fried rice filling into the center of the omelet. Fold the omelet over the filling and shape with a spatula. Cook for another minute.

Transfer Omurice to a plate, drizzle with ketchup or sauce, and serve warm.