Season chicken with salt and pepper. Heat oil and 1 tbsp butter in your favorite pan over medium-high.
Add chicken and cook until golden brown on each side. Continue to flip and cook if necessary until a thermometer inserted into thickest portion reaches 165F (~4 min per side).
Transfer chicken to a plate and set aside. Reminder, not to wipe out the pan. The reserved bits are what makes this sauce special.
Lower heat to medium. Add mushrooms, a pinch of salt, and 1 tbsp butter.
Cook, stirring occasionally, until mushrooms begin to brown (5 min).
Add shallot and cook, while stirring until tender (3 min).
Add brandy (or cognac) and cook while using a wooden spoon to scrape up the fond, until liquid is nearly evaporated (~15-30 seconds).
Add chicken broth, cream, 1 tbsp lemon juice, mustard, and Worcestershire. Cook, stirring frequently, until sauce reduces slightly (~3-4 min).
Add parsley and season to taste with salt and pepper. Remove from heat.
Transfer the chicken and its juices back into the sauce in the pan. Enjoy!
