Cut and Season Chicken: Pat chicken breasts dry with paper towels and cut into 1-inch pieces. Transfer pieces to a large bowl, sprinkle with salt and pepper, then toss to evenly coat.
Dredge Chicken in Flour: Place flour in a shallow dish or bowl. Coat chicken pieces individually by gently pressing each piece into the flour until all sides are evenly covered. Shake off excess flour and transfer each coated piece to a plate. (This ensures each chicken bite is evenly coated, providing a better crust and browning.)
Heat Skillet: Heat olive oil in a large skillet over medium heat. Allow oil to get hot before adding chicken.
Brown Chicken: Carefully add floured chicken pieces to the hot skillet in a single layer. This part can get messy, so be careful, and consider using a splatter guard if you have one. Cook for 3-4 minutes per side, until golden brown and cooked through (165 degrees F in the center of the thickest piece). If the pan gets too dry or starts to smoke, lower the heat slightly or add another splash of oil. Work in batches if needed to prevent overcrowding, and add a little more oil to skillet as needed. Transfer cooked chicken to a clean plate.
Cook Garlic: Reduce heat to medium-low. Add butter to the same skillet and allow it to melt. Add minced garlic and cook for 30 seconds, stirring constantly so it doesn’t burn. If garlic starts browning too quickly, briefly remove the skillet from heat to cool it down.
Combine Chicken and Parmesan: Return the cooked chicken to the skillet. Stir to coat pieces in garlic butter. Sprinkle Parmesan cheese over the chicken and stir again until evenly coated and slightly melted. Cook an additional 1-2 minutes, stirring constantly, until everything is warmed through.
Serve: Transfer chicken to a serving platter or bowl. Garnish with chopped parsley if using, then serve immediately.