In a large skillet over medium heat, add butter and 1 tbsp. oil. When it starts shimmering, add sliced onions and season with ground sea salt. Stir well and sauté for 2 minutes.
Add pressed garlic and freshly ground black pepper. Stir to blend, cover and cook for 10 minutes, stirring every 2 minutes.
After 10 minutes, uncover, stir again and cook for 20 minutes, stirring often.
When onions are nice and soft, increase the heat to high and sauté them until light brown; about 1 ½ minutes – if prefer darker, sauté them longer.
Transfer the onions to a bowl while looking after the liver.
Cut liver into 3 to 4-inch pieces; set aside.
In a shallow dish, add flour, hot paprika, garlic powder and freshly ground black pepper; mix to combine.
Working with one piece at a time, coat the liver with the flour mixture, shake off any excess flour and place on a plate while working with the others.
Add remaining 1 tbsp. oil to the same skillet over medium heat. When hot, add seasoned liver pieces and cook until nice and brown, about 1 ½ to 2 minutes per side depending on the thickness.
When done, top the pieces with caramelized onions and serve with mashed potatoes – don’t forget the ketchup!