Cook jasmine rice in your method of choice. I use a rice cooker. Make the sauce by combining maple syrup, soy sauce, mirin, water, garlic powder, pepper, and onion powder and set aside.
In a large skillet over medium-high heat, add a splash of oil and add the beef to it. Cook until 80-90% browned and drain any excessive liquid in the pan.
Push the beef to the side of the pan, making a large enough space in the middle of the pan for a bowl of rice. Add 1 tbsp butter to the middle of the pan and let it melt for a few seconds. Add mushrooms and cook down for a few minutes.
Tightly pack around 3 cups of rice into a bowl and invert it into the middle of the pan, over the butter.
Remove the bowl, drizzle the sauce over the rice and beef, and then top with the corn. Let everything cook together, untouched for 2 to 3 minutes. The bottom of the rice will get nice and crispy while the sauce cooks with the beef.
Top off with the rest of the butter and green onions before serving.
