The time needed to dry different herbs can vary quite a lot depending on your microwave, the size of the leaves, the type of herb (mint is the quickest to dry, parsley the slowest), and the quantity you are drying so it's best to do a trial run before sacrificing a whole bunch.
1. Using 1 sprig at first, place on a plate and microwave on high for 30 seconds. Remove sprig from microwave and wait 1 minute to see if it's completely dry (and won't bend without breaking). If not yet dry, keep microwaving for 10-20 second intervals until it crumbles easily. (Large basil leaves can take up to 2 minutes, while smaller leaves can be completely dry in 30 to 50 seconds.)
2. Once you’ve determined the optimum drying time, place fresh herbs in a single layer on a plate, being careful not to crowd them. Microwave on high until dry.
3. Store dried herbs (crumbled if you like) in sealed containers or plastic bags in a cool, dark place.