Mushroom, Asparagus and Bell Pepper Stir-Fry

Ingredients

• ¼ cup vegetable oil
• 1 red onion, julienne sliced
• 1 tablespoon brown sugar
• 1 tablespoon white wine vinegar
• salt
• 6 champignon mushrooms
• ¼ zucchini
• ½ yellow bell pepper, sliced
• ½ red bell pepper, sliced
• pepper
• ½ teaspoon chili flakes
• ½ teaspoon oregano, dried
• 4 asparagus sticks
• 1 ounce parmesan