void MyClass::foo()
{
   ... bla-bla
   OurCoolUtils::Logger::getInstance()->write("Finish bla");
   ... boo-boo
}

MyClass::MyClass(........, ILogger* logger) 
  : .... logger(logger)
{
  ...
}

void MyClass::foo()
{
   ... bla-bla
   logger->write("Finish bla");
   ... boo-boo
}