Efficient 1 watt Led circuit
Edit: A homemade 555 switching regulator is not the most efficient (switching device is forced to drop voltage that the LED can't use) or safest (no current protection) way to light your LED. The least efficient way is to put an appropriately sized resistor in series for your particular power supply. The most efficient method which might also give you dimmer control would be a buck regulator (uses a magnetic field to "level shift" your voltage efficiently, if you need less voltage ie LED forward voltage, the buck converter will draw less current from the source so Pout/Pin is high).

You may also be using the 555 because you have heard that the pulses appear brighter to the human eye than continuous light, see this thread: 
Does pulsing an LED at higher current yield greater apparent brightness?

So to recap: efficient = buck converter; easy = resistor (but for what it's worth, the lower the voltage supply the more efficient it'll be because the power supply is likely acting like a pre-set buck regulator before you attach your big hot resistor to it); fun but not reliable = 555 with semiconductor output stage, see this thread for details on how to drive an LED without current protection:
Do I really need resistors when controlling LEDs with Arduino?

Original reply: You can absolutely use a 555 to drive the base of a transistor! You probably want to set up an emitter follower (boost the current) output stage if you can afford the .6 volt drop.