Bring a pan to medium high heat. No need to add any fat/oil/butter. 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 1/4 tsp sea salt and a pinch of black pepper. Cook for ~2-3 minutes uncovered, flip and cook ~2-3 minutes or until browned. Add balsamic vinegar to the pan. The pan may "hiss". Continue cooking for an additional minute.
Toss cooked mushroom with chopped pistachios. Add sea 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!