PaulS:
You need to add a line to the header file that says that lcd is an instance of the LiquidCrystal class. The, it needs to be instanced/valued at the same time as the constructor of your class is called:MenuLCD::MenuLCD(byte rs, byte enable, byte d4, byte d5, byte d6, byte d7, String intro, MenuItem _menu), lcd(rs, enable, d4, d5, d6, d7)
to be honest, i didn't understand. how can i say that lcd is an instance of LiquidCrystal?