Start by preheating your oven to 375°F (190°C). While it warms up, line a baking pan with parchment paper to prevent sticking and facilitate easy cleanup.

Slice the poblano peppers in half lengthwise and carefully remove the seeds. Lay the halved peppers cut side up on the prepared baking sheet.

In a skillet, heat a drizzle of oil over medium heat and add the ground beef. Cook for about 5 minutes, breaking it apart as it browns. Mix in the chopped onion and sauté for an additional 3 minutes until softened.

Whisk together Kikkoman® Teriyaki Marinade with cornstarch in a small bowl. Pour this mixture into the skillet with the beef and onions, stirring well. Allow it to simmer for about 2 minutes until the sauce thickens slightly.

Incorporate the chopped broccoli florets and brown rice into the beef mixture, stirring well to combine everything evenly.

Carefully spoon the hearty beef mixture into each roasted poblano half, packing it generously.

Cover the stuffed peppers with aluminum foil and place the baking pan in the preheated oven. Bake for approximately 20 minutes.

Remove the foil and allow the peppers to cool slightly before serving. Garnish each pepper with freshly chopped cilantro.