Preheat the air fryer to 350°F (175°C).
In a small bowl, combine the softened butter, minced garlic, 2 teaspoons of the chopped parsley, and the grated Parmesan (if using) until evenly mixed.
Spread the garlic butter mixture evenly over one side of each baguette slice using a knife or pastry brush.
Arrange the slices in a single layer in the air fryer basket without overlapping.
Air-fry for 5–7 minutes, or until the edges are golden and the tops are bubbly and crisp.
Remove the garlic bread, sprinkle the remaining 1 teaspoon chopped parsley over the slices, and serve warm.