Marinate chicken in buttermilk in a Ziploc bag for 30-60 minutes.
Create breading process with 3 separate shallow dishes or bowls. In the first dish, mix flour, 1 tsp salt, 1 tsp garlic powder, and ½ tsp pepper. In the second dish, mix egg and 1 TB water. In the third dish, mix Panko, 1 tsp salt, and ½ tsp pepper.
Coat chicken in flour (first dish), dredge in egg mixture (second dish) then coat in panko (third dish). Repeat with each chicken breast and place on a baking sheet.
In a large skillet over medium high heat, melt butter and olive oil. Place 2 chicken breasts in the pan and brown (about three minutes on each side). continue cooking until chicken is cooked all the way through. Repeat with the last two chicken breasts. Place on paper towel lined plate to drain excess oil.
Make dressing by whisking lemon juice and olive oil. Season with salt and pepper.
Lightly coat arugula with lemon vinaigrette and scoop onto each breast. Top with shaved parmesan and serve warm. ENJOY!