Step 1
First, prepare the ingredients.
Step 2
In a medium skillet over medium heat, melt 45g of butter. Add the diced onion and sauté until soft, which should take about 5 minutes. Stir in the sugar, then reduce the heat to low and continue to cook and stir until the onion is very tender and brown, which will take approximately 25 to 30 minutes. Transfer the caramelized onions into a small bowl and reserve the skillet.
Step 3
While the onions are caramelizing, rinse the calf liver and remove the thin outer membrane. Then, slice the liver into 1/2 to 1cm thick slices.
Step 4
Dredge the liver slices in flour, ensuring that they are evenly coated.
Step 5
In the same skillet, heat the remaining 15g of butter over medium heat. Add the liver slices and cook until browned, which should take about 1 to 1 1/2 minutes per side.
Step 6
To serve, arrange the sautéed calf liver on a platter and top with the caramelized onions.