Whether you're talking about a porcini, shiitake, chanterelle - or the even the common button mushroom found in the supermarket - properly cleaning and storing your mushrooms is the key to freshness.
Keep mushrooms fresh by storing them correctly. Mushrooms like air, so don't close them up in a plastic bag, which is a quick way to make them sticky, squishy and unappetising! Instead, place them in a paper bag or on a tray in the fridge covered with a damp piece of kitchen roll.
Here's another freshness tip: Don't wash mushrooms until you're ready to use them.