First of, frozen berries do not need to be thawed when used in baked goods. If you're making muffins or a cobbler or a pie, just throw the frozen berries into the batter or the bowl the same way you would with fresh berries and be done with it!
If, however, you want to try and thaw berries so that they can be used in dishes as fresh berries would be—as garnishes or in salads—you can thaw them using this method to best retain their shape and appearance.
They will not be quite as lovely as fresh berries, but they are the most likely to come close!
- Place the berries (about 1 cup maximum at a time) in a single layer with plenty of space between the berries on a paper towel-lined microwave-safe plate.
- Put them in a microwave on "defrost" for 30 seconds. Check the berries and repeat until the berries are defrosted (about 30 seconds for raspberries and blueberries, 1 minute for blackberries, and up to 2 minutes for strawberries).
- Immediately remove berries from the microwave to stop any cooking. The berries should look lightly frosted and have retained their distinctive shape.
- Carefully lift the berries off the paper towel and place them as a garnish or in a salad or however you were planning on using the frozen berries as fresh.
NOTE: Thawed frozen berries will be more delicate than actual fresh berries, so they will start to fall apart quite quickly if tossed around in a fruit salad, for example.
Treat them accordingly if you want them to keep their shape.
Again, the times when you need to defrost berries before using them are limited. Any time berries are being baked or cooked—including being turned into a sauce or jam—they don't need to be defrosted first. The baking or cooking will un-freeze them so quickly, that there's no need to defrost them first.
There are even cases where frozen berries are preferable: most particularly, when making smoothies, where using frozen berries will thicken the smoothie in a most pleasing fashion (a nice little trick for people who for whatever reason prefer to make smoothies without bananas in them!).
A final note on frozen berries: when quickly frozen in prime condition, frozen berries behave just as deliciously in recipes as fresh berries. Extensive side-by-side testing of baked goods and smoothies supports this claim! So when the market is full of perfectly ripe, in-season berries, be sure to buy some extra and freeze them—your future self will thank you!