Season the chicken breast generously, on both sides, with the garlic powder, salt and pepper. If your chicken breasts are very thick, slice them in half horizontally first.
Add the flour to a shallow plate or bowl, then add the eggs to another bowl and beat them with the milk or cream.
Dredge the chicken breasts in the flour, tapping off the excess and place on a plate. Once the chicken breasts have been coated in the flour, add 2 tablespoons of butter to a large skillet over medium heat.
Dip the chicken into the egg mixture, letting the excess drip off and then place into the hot skillet. Repeat with the remaining chicken breasts.
Cook for 3-4 minutes on each side until golden brown and then remove the chicken from the skillet to a plate and cover with foil.
Carefully pour in the wine to deglaze the skillet and let reduce for 1 minute. Add the chicken stock, lemon juice and the remaining tablespoon of butter, stirring to combine. Bring the sauce to a simmer and cook for 5 minutes, then add the cornstarch mixture and whisk to combine with the sauce.
Bring the sauce back to a simmer, add the chicken breasts back to the skillet and top with the fresh lemon slices.
Simmer the chicken for 8-10 minutes over low heat, spooning the sauce over the chicken as it cooks. Cover to keep warm or serve immediately.