Prep Work:

1. Combine beef broth, chicken bouillon, soy sauce, onion powder, mustard powder, and thyme in a bowl. Set aside.
2. Mix cornstarch with 3 Tablespoons of cold water in a sealable container and shake to combine. Keep in a cool place.
3. Gently rinse mushrooms and pat them completely dry. Slice if needed.
4. Slice the chicken lengthwise into 2-3 thinner pieces. Pound with a meat tenderizer if needed, aiming for 1/2-inch thick slices.

Cook the Mushrooms:

1. Melt butter in a large pan over medium-high heat. Add mushrooms and let them brown on each side for 3-4 minutes without stirring.
2. Sauté in batches if needed, leaving space around the mushrooms for better browning. Add more butter or olive oil if necessary.
3. Remove mushrooms once golden brown and set aside on a plate.

Dredge and Sear the Chicken:

1. Lightly season both sides of the chicken with salt and pepper. Dredge in flour and shake off any excess.
2. Heat olive oil in the same pan over medium-high heat. Add 3 pieces of chicken, leaving space around each. Cook for 4-5 minutes per side until a golden crust forms.
3. Remove and set aside. Repeat with the remaining chicken pieces.

Pro Tip: Adjust heat as needed during cooking, and avoid moving the chicken too much while it sears to achieve a nice crust.

Deglaze the Pan:

1. Turn off the heat and remove any excess oil, leaving the brown bits (fond) in the pan for flavor.
2. Add white wine and garlic to the pan. Turn heat to medium and scrape the bottom of the pan with a silicone spatula.
3. Let the wine bubble gently and reduce by half, about 4 minutes.

Finish the Sauce:

1. Add the beef broth mixture to the pan. Increase heat slightly to bring it to a gentle boil. Let it bubble and reduce for 10 minutes.
2. Shake the reserved cornstarch mixture and slowly stir it into the bubbling sauce. Stir continuously until the sauce thickens. Reduce heat to low.
3. Gradually stir in the heavy cream. Add the mushrooms back to the pan.
4. Add the chicken along with any juices from the plate. Spoon the sauce over the chicken. Cover partially and let it heat through for about 5 minutes.