Marinated Mushrooms

INGREDIENTS

• 1 1/2 pounds button mushrooms
• 1 1/2 tablespoons salt
• 1 1/2 tablespoons white sugar
• 1/4 teaspoon crushed red pepper
• 1/4 teaspoon black pepper
• 1/4 teaspoon dried oregano
• 1/2 teaspoon monosodium glutamate (such as Ac'cent®)
• 1 teaspoon chopped garlic
• 1 onion, chopped
• 3/4 cup white vinegar
• 1/3 cup olive oil