Preheat your air fryer to 400°F (200°C) for 3-5 minutes. This ensures the fries start cooking immediately when placed inside.
Spread the frozen fries in the air fryer basket in a single layer. Avoid overcrowding to ensure proper air circulation and crispy results. Depending on your air fryer size, you may need to cook in batches.
Cook the fries for 10-15 minutes, shaking the basket halfway through cooking time. Different brands and styles of fries may require slightly different cooking times, so start checking at the 10-minute mark for your desired crispiness.
While the fries are cooking, prepare the garlic butter. Place the butter in a microwave-safe bowl and melt it for about 30 seconds. Add the minced garlic, salt, pepper, and dried oregano (if using) to the melted butter and stir to combine.
When the fries are golden and crispy, transfer them to a large bowl. Immediately pour the garlic butter mixture over the hot fries and toss gently until all fries are coated.
Sprinkle with fresh parsley and Parmesan cheese (if using) while the fries are still hot. The residual heat will help melt the cheese slightly and release the aroma of the herbs.
Add a pinch of red pepper flakes if desired and give everything one final toss. Taste and adjust seasoning if needed.
Serve immediately while hot and fragrant for the best flavor and texture experience.