Cut the chicken into 1-inch chunks and place them in a bowl. Season generously with salt and pepper, tossing to coat evenly. This ensures the seasoning penetrates the meat rather than just sitting on the surface. While the chicken seasons, mince the garlic and grate the parmesan cheese—having these ready will let you work quickly once the chicken hits the pan.

Melt 2 tablespoons of butter in a large skillet over medium heat until it foams slightly. Once hot, add half of the seasoned chicken in a single layer—don't crowd the pan, as this allows proper browning. Cook for 4 minutes without stirring, letting the chicken develop a golden crust. Flip each piece and cook for 2 minutes more until the second side is golden. Transfer this batch to a clean plate.

Add 1 tablespoon of butter to the same skillet and let it melt. Add the remaining seasoned chicken in a single layer and repeat the searing process: 4 minutes on the first side without stirring, then flip and cook 2 minutes more until golden. I like to use the same pan without cleaning it because those browned bits add incredible flavor to the final sauce.

Return all the seared chicken from both batches to the skillet and reduce the heat to low. Add the remaining 1 tablespoon of butter and the minced garlic, stirring constantly for about 1 minute until the garlic becomes fragrant but not browned—this prevents it from turning bitter. Remove the skillet from heat and quickly stir in the grated parmesan cheese, parsley, red pepper flakes, and lemon juice until everything is evenly coated and melted.