Wash liver, put in a zip bag with milk and put in the ice box for an hour or so.
Remove liver from bag, season with salt and pepper. Dust the liver with flour in a pan and leave them in the flour.
In a medium sized skillet, sauté the onions in butter until slightly brown and remove and drain Drain any leftover butter in a cup. While doing this, dust the liver once more and set on a plate. Let the liver rest a few minutes.
Add the cooking oil to the same pan and heat until ready to fry inches Put two or three pieces of liver in the oil leaving a 1" space between each. Keep the oil at a good temperature to maintain frying. Fry liver on each side until golden brown and remove. You are not trying to fully cook it, just brown it.
Take the liver out, put it a plate and cover it with foil. Pour the oil out into the the cup with the butter in it to make about 1/4 cup; pour this back in the pan and put on a medium fire. Add enough flour to make a small medium brown roux. Add chicken stock (or water) enough to make the roux a medium thickness. Be sure to boil this and sprinkle some garlic powder in it.
Remove roux and in the same pan return liver, onions (regular and green) and roux. Cook on medium fire for about 15 minutes (stirring every 5 minutes) or so or until liver is done but not overdone.