Place each chicken breast flat on a cutting board. Slice horizontally through the middle to create two thinner cutlets, giving you 4 total. Pound any thick spots with a meat mallet until each piece is about 1/2 inch thick throughout.

In a small bowl, combine garlic powder, mixed herb, salt, and black pepper. Season both sides of each cutlet generously, pressing so the seasoning adheres.

Heat olive oil and 1.5 tbsp butter in a cast-iron skillet over medium-high heat. Once the butter foams, add chicken cutlets without overcrowding. Sear 3 to 4 minutes per side until golden brown and internal temperature reaches 165°F. Transfer to a plate and cover loosely with foil.

In the same skillet over medium heat, melt 1 tbsp butter. Add minced garlic and saute for 30 seconds until fragrant. Watch closely to avoid burning.

Sprinkle flour over the garlic and stir constantly for 30 seconds to create a roux base and eliminate the raw flour taste.

Pour in chicken stock slowly while whisking constantly to prevent lumps. Continue whisking 2 to 3 minutes until the sauce thickens and coats the back of a spoon.

Reduce heat to medium-low. Add room temperature sour cream and ranch seasoning, whisking until you have a glossy, smooth sauce. If the sauce looks grainy, keep whisking over low heat until it comes together.

Nestle the chicken cutlets back into the pan. Spoon sauce over each piece, garnish with fresh parsley, and serve immediately.