For the chicken:

If the chicken fillets are not uniform in size (thicker in spots), wrap them in plastic wrap and pound with a flat meat mallet.

Place the flour, salt, pepper, and garlic powder in a shallow dish.

In another shallow dish, whisk together the eggs and milk.

In a large skillet over medium-high heat, melt the butter and olive oil together.

Dredge each chicken fillet in the flour mixture and then into the egg wash.

Lie the breaded chicken fillet in the hot skillet.

Repeat with the remaining 3 chicken fillets.

Cook until golden brown, flip and cook the other side until golden and the chicken is cooked through.

Remove the chicken to a plate and set it aside.

For the sauce:

In the same skillet, melt 1 tablespoon of the butter over medium heat.

Add the lemon slices in a single layer and cook until the slices begin to brown – about 3 minutes.

Remove the lemon slices to the same plate as the chicken.

Add the remaining butter into the pan.  Toss in the onions and garlic, and stir to coat with the butter. Saute, stirring often, until the onions turn translucent – about 8 minutes.

Sprinkle in the flour, stir and cook for about a minute.

Whisk in the wine and simmer another 2 minutes.