First let’s start with this, searing does not seal in the juices.  This mistaken idea has been around since the 1800’s..  When heat is applied to a protein (meat), the protein molecules start to unravel. As they unravel, juices are released.  Those juices are reducing and browning/caramelizing in the pan.  This is not to say that browning isn’t good.  It creates layers of flavor in the fond (browned bits).  Also the connective tissue around the muscle fibers start to shrink above 160°F (71°C) squeezing the juices out. That is why you can cook a piece of meat in liquid and if you rush it by boiling it, it will be dry and tasteless.

Leave room when you are doing mushrooms and onions too. These are sliced shiitake mushrooms

When browning meat, poultry, mushrooms, etc. the key is not to crowd the pan.  Leave room for the juices released by the high heat to evaporate.  We’ve all been in a hurry and added too much to the pan and wound up with a gray stew instead of anything getting brown and delicious.

Leave space for moisture to evaporate. Notice the browned bits (fond) that you will deglaze after the meat is done browning

 Once you have finished browning you will notice browned bits in the bottom of the pan. These are flavor gold. Deglaze the pan, which is only adding some wine, stock, or even water to the pan and scraping them up to dissolve in the liquid.  Add this to your stew or use it as a start to a pan sauce. Added bonus, your pan is almost clean!