Place chicken breasts between two pieces of plastic wrap. Using a meat mallet, pound each breast to an even ½-inch thickness. This ensures even cooking and prevents dry spots. Pro tip: Pat the chicken dry with paper towels before pounding—this helps it brown better and ensures a golden crust in the skillet.

Season both sides of the chicken generously with kosher salt and fresh black pepper. Let sit for 5 minutes while you prepare the mushrooms. Pro tip: Seasoning ahead allows the salt to penetrate the meat for better flavor throughout.

Heat 1 tablespoon of olive oil in a 12-inch skillet over medium-high heat. Once shimmering, carefully place chicken breasts in the pan without moving them. Pro tip: Don't crowd the pan and don't move the chicken around—let it develop a golden crust for 6-7 minutes before flipping.

Cook for 6-7 minutes until golden brown, then flip and cook another 5-6 minutes until the internal temperature reaches 160°F. Transfer to a plate. Pro tip: The chicken will finish cooking when we add it back to the pan with the sauce, so you want it just under the safe internal temperature to prevent overcooking.

Add the remaining 1 tablespoon olive oil to the same skillet. Add sliced mushrooms and cook for 4-5 minutes, stirring occasionally, until they release their moisture and begin to brown. Pro tip: Don't stir too frequently—let the mushrooms sit undisturbed for a minute or two between stirring to develop that beautiful golden color and concentrated flavor.

Add minced garlic and cook for 1 minute until fragrant. Scrape the bottom of the pan with a wooden spoon to release all those flavorful browned bits (fond). Pro tip: This fond is liquid gold for your sauce—it contains concentrated chicken and mushroom flavors that make the difference between good and exceptional.

Pour in the chicken broth, scraping the pan well to incorporate all the fond. Add thyme and bring to a simmer. Cook for 2 minutes to reduce slightly and concentrate flavors. Pro tip: If using fresh thyme instead of dried, add it after you remove from heat to preserve its delicate flavor.

In a small bowl, whisk together sour cream, Dijon mustard, and lemon juice until smooth. Reduce heat to low and slowly whisk the sour cream mixture into the simmering broth. Pro tip: Tempering the sour cream by slowly adding it prevents curdling. Never let the sauce boil after adding sour cream—keep it at a gentle simmer.

Return chicken breasts to the skillet, nestling them into the mushroom sauce. Simmer for 5-7 minutes until the chicken reaches a safe internal temperature of 165°F and the sauce coats the back of a spoon. Pro tip: If you prefer a thicker sauce, whisk together 1 teaspoon cornstarch with 1 tablespoon cold water and stir it in during this final simmer.

Taste and adjust seasonings with salt, pepper, or lemon juice as needed. Garnish generously with fresh parsley and dill. Serve immediately over egg noodles, rice, or mashed potatoes. Pro tip: The fresh herbs add brightness to this rich dish—don't skip the garnish, as it makes a significant difference in the final flavor profile.