If you really want to burn calories both during and after your ride, do both. Interval training involves short bursts of intense effort followed by brief rest periods. There are numerous variations but if you have a FitBit or similar pulse monitor, here is a good one: Push hard and maintain 85%+ of your max heart rate for one minute. Reduce the effort to a comfortable pace and let your heart rate come back down to <70%, then hit it again. Do this for 5-10 repetitions to start and then finish the ride at a comfortable pace to cool down. Of course you don't need a heart rate monitor to do intervals, they can be as simple as ride hard for a minute, spin comfortably for a minute and repeat.