Unlike most loose leaf teas, puerh cakes and other compressed tea cakes need to be carefully pried to loosen or broken apart before you brew them.
Compressed tea cakes or bing cha originated in China over a thousand years ago. They're still very practical for storing, transporting, and aging tea. This is why white2tea presses cakes of white tea, black tea, oolong, and of course puerh.
This advice applies to any pressed tea in cakes (bings), mini cakes, tuo cha (tea pressed in the shape of a bell, dome, bird's nest, or mushroom), and puerh tea bricks. It does not apply to single-serving mini tuos or brewing puerh tea balls ("dragon balls").
Tea Knives, Puerh Picks, and Sharp Tools: A Word of Caution
A tea knife or puerh pick is a special tool made for breaking apart tea cakes. A letter opener, butter knife, pocket knife or flathead screwdriver can serve the same purpose.
Tea tools are made for poking and prying, not cutting, but they're pointy. Breaking or prying apart highly compressed cakes requires force. It's safest to do this holding the tea cake on a cutting board with your limbs out of the way.
Cakes vary a lot in terms of compression. Some are loose enough to pry with a fingernail. Some cakes need a little encouragement with a tool. Certain decorative or commemorative cakes with ornate pressed designs may be pressed so tight that you're safer using pliers or a vise grip to break off chunks.
How to Break Apart a Tea Cake
You've got your tea cake and tea pick ready and you're standing over a cutting board or sturdy surface just in case. If the cake's unopened, start by removing the paper wrapper (it's reusable and helps you identify the cake, so try not to destroy it).
Think of the cake as being made up of flat layers of long, thin leaves. The trick is to work the tea pick into the narrow edge or side of the tea cake as gently as possible to get between the leaf layers. Try to avoid breaking leaves.
Push the pick all the way into a few different spots and you'll start to feel the cake loosening up. At this point, you might be able to use your fingers to pull off some chunks of compressed leaves. Set aside any small chunks to weigh them. You might be done.
If you get a larger chunk off the cake instead, you can separate it further with your fingers. You might need to loosen the chunk with the pick first.
The cake might not be coming apart at all. You might be struggling to even insert the tea pick. That means you're dealing with a more compressed cake. Hold it firmly and with your body parts safely out of the way, use more pressure to insert the pick.
Wiggle the fully inserted pick in all directions. Reinsert and repeat until you start getting some loose layers or chunks.
Once you've set aside what you'll be drinking put any stray chunks, leaves, crumbs or dust back into your tea storage with the rest of the cake.
How to Brew a Puerh Cake
Your puerh tea session starts with a chunk from your puerh cake. You don't need to loosen it more or break it apart further to brew it. You'll rinse it with boiling water to help the leaves expand or "wake up," then you'll steep as normal.
For gongfu style or grandpa style tea you rinse the leaves directly in your gaiwan, teapot, or mug, then discard the rinse water. Most teas do fine with one rinse, but more compressed teas (puerh or other types) can benefit from two or three rinses. The idea is to activate the leaves without much extraction, which works out to about 5 to 30 seconds per rinse.
If you still see air bubbles escaping, you can leave the tea in a little longer or rinse again. If the rinse water is darker than a pale clear-yellow, you may have overdone it a little bit (stop rinsing).
For infuser baskets and other western-style methods, rinse to allow the tea to expand, then steep as normal. You can do this inside the basket or before adding it to the basket. Check that you've still got enough room in the basket after the rinse step.