Pound chicken breasts so that they're approximately 1/2 inch thick.
Season chicken breasts on both sides with salt & pepper.
Melt 2 tablespoons butter in large skillet and add chicken breasts to pan.
On medium to medium-high heat, cook chicken breasts for approximately 8 minutes on each side until juices run clear and they are fully cooked on the inside and golden brown on the outside.
Remove chicken from skillet and set aside on a large plate with tin foil tented over top to keep it warm.
Add 2 tablespoons of butter to skillet and add sliced mushrooms. Saute over medium heat for 3 minutes or until golden brown.
Remove sauteed mushrooms and set aside.
Add brandy and minced garlic to skillet over medium heat and scrape up the browned bits. Cook for 4 minutes or until the brandy has been reduced by half.
Add the last 2 tablespoons of butter to the brandy mixture and stir over medium heat until the butter is melted.
Add the heavy cream, salt & pepper to the brandy mixture and use a whisk to combine all ingredients. Simmer for 4 minutes or until the sauce has thickened.
Reduce heat to medium-low and add the mushrooms, sun-dried tomatoes, artichoke hearts, & walnuts to the brandy sauce and mix well.
Then add the chicken breasts and spoon the sauce over them while simmering for 2 additional minutes.