Steak Teriyaki Tailgate Style

2/3 cup soy sauce
1/4 cup mirin
1/4 cup rice vinegar
1/4 cup sugar
1 tablespoon freshly grated ginger
2 cloves garlic, minced
2/3 cup beer
2 1/2 pounds flank steak

1. For the teriyaki marinade, combine the soy sauce, mirin, vinegar, sugar, ginger, garlic and beer in a small saucepan. Cook over high heat until the mixture reduces by half. Let cool.

2. Place the flank steak and teriyaki marinade in a plastic bag, seal tight. Place the bag in a cooler with ice packs and let the steak marinate on the way to the game.

3. When you get to the parking lot, preheat a portable grill.

4. Cook the steak on each side until it is cooked through, about 4 to 8 minutes per side, depending on the desired doneness.