Bring a pan to medium high heat. No need to add any fat/oil/butter but feel free.
Throw the quartered mushrooms straight into the hot pan and fry them as is. Mushrooms let go of a lot of liquid so it will be fine. You may have to do this in two different batches as you want to try and crisp up the mushrooms on the outside and not steam them.
Add pinch of salt and a pinch of black pepper. Cook for ~3-4 minutes uncovered and undisturbed and flip when browned.
Cook again for 3-4 minutes undisturbed or until browned.
Add balsamic vinegar to the pan. The pan may "hiss".
Turn the pan off and cook the mushrooms for an additional 30-60 seconds or until balsamic vinegar is absorbed. Here is another good time to add oil or butter if you prefer.
Add the chopped pistachios.
Add salt to taste and top with sliced basil. Happy Eating! Beckie
Notes
Mushrooms not browning? Try not moving them in the pan to much. They need time to make the crust.
Chopping nuts can be difficult because they want to "slip away". Place in a sealed ziploc bag with no air and hit the bag/nuts with the back of a large spoon. Get some aggression out!
Wanna make this a main meal? Cool, add mushrooms to cooked pasta and add a little heavy cream and Parmesan cheese for a creamy sauce.