Rinse the liver in a colander under cold water and drain it well on kitchen paper. Put 2 teaspoons of the flour in a large bowl and season with plenty of salt and pepper. Add the liver to the bowl and turn it in the flour until lightly coated.
Melt half the butter with the oil in a large non-stick frying pan over a medium heat. Tap the excess flour off each slice of liver and add them to the pan using tongs. Cook for 1½–2 minutes on each side until lightly browned but not completely cooked through, then pop them on to a plate.
Turn down the heat and melt the remaining butter in the same pan. Add the sliced onion and cook for a minute or so, stirring to separate the layers. Next, add the bacon and cook together for another 5 minutes or until the onion is softened and pale golden brown, stirring often.
Sprinkle the remaining flour over the onion and bacon and cook for a few seconds, stirring. Pour the hot stock slowly into the pan, stirring constantly. Bring to a simmer, stir in the ketchup and cook over a medium heat until the gravy is thickened and glossy.
Put the liver back in the pan and heat it through in the onion gravy for 2–3 minutes until hot, stirring. Season to taste with salt and pepper. Serve the liver and bacon with a small portion of mashed potatoes and lots of freshly cooked greens.
Comments will be approved before showing up.