Fill and bake tartlets
Preheat the broiler (grill). In a large saucepan over medium heat, warm the oil. Add the garlic and cook until lightly golden, about 1 minute. Add the spinach and cook until just wilted, about 2 minutes. Season with salt and pepper. Place equal amounts of the spinach mixture in each tartlet shell, top with the cheese, and sprinkle with the pine nuts. Broil (grill) until the cheese is golden, 2–3 minutes. Transfer the tartlets to a wire rack and let cool slightly. Remove the pan rims, slide the tarts onto plates, and serve warm.