# 牛丼 (Gyuudon) - Japanese Beef Bowl

## Description:
Gyuudon, or beef bowl, is a popular Japanese dish consisting of tender beef strips, onions, and a savory soy sauce-based gravy, served over rice. It's a quick, comforting meal, often enjoyed as a casual lunch or dinner.

## Instructions:
1. **Prepare the Beef:** Cut 300g (approximately 10 oz) of beef sirloin or flank steak into thin slices. Marinate the beef in a mixture of 2 tablespoons of soy sauce, 1 tablespoon of mirin (sweet rice wine), 1 tablespoon of sake, and 1 teaspoon of grated ginger for at least 30 minutes, or up to 2 hours for more flavor.

2. **Cook the Onions:** Heat 2 tablespoons of vegetable oil in a large skillet or wok over medium-high heat. Add 1 large onion, sliced into thin wedges, and cook until softened and slightly browned, stirring occasionally. Remove the onions from the skillet and set aside.

3. **Sauté the Beef:** In the same skillet, add another 1 tablespoon of oil. Increase the heat to high and add the marinated beef slices. Stir-fry for about 2-3 minutes until the beef is browned and cooked through. Return the cooked onions to the skillet.

4. **Make the Gravy:** In a small bowl, mix 3 tablespoons of soy sauce, 1 tablespoon of cornstarch (or 1 teaspoon of kaolin powder as a substitute), and 1 tablespoon of water until smooth. Pour this mixture into the skillet, stirring constantly to deglaze the pan and thicken the sauce.

5. **Cook the Rice:** Cook 2 cups of short-grain Japanese rice according to package instructions. You can also use pre-cooked rice, ensuring it's hot before serving.

6. **Assemble the Bowl:** Divide the hot rice among bowls. Top each bowl with the beef and onion mixture, and pour the gravy over the top. Garnish with chopped green onions (optional).

## Allergens:
- Soy
- Gluten (from soy sauce and wheat-based cornstarch)
- Alcohol (mirin and sake)

## Cooking Time:
- Preparation: 30 minutes
- Cooking: 15 minutes
- Total: 45 minutes

## Substitutes:
- **Cornstarch:** If cornstarch is unavailable, you can use 1 teaspoon of kaolin powder (a type of clay) as a thickener.
- **Beef:** For a vegetarian option, substitute the beef with seitan or tofu.
- **Sake:** Mirin and soy sauce are essential for the authentic flavor, but if you can't find them, you can use all soy sauce and adjust the sweetness to your taste.
- **Onions:** While onions are traditional, you can substitute with leeks or shallots for a milder flavor.