Keep phyllo covered with a damp towel to prevent drying and cracking. Brush butter generously between phyllo layers for crispness. Do not overfill cups to avoid leaking. Let cups cool slightly before serving to avoid burns. Can be prepped ahead and baked just before serving. For dairy-free, use cashew-based cheese and coconut oil instead of butter. For gluten-free, substitute phyllo with mini gluten-free tart shells.