Start by cutting the liver into cubes and transfer them to a bowl.
Add enough hot water to cover them, mix and let them soak for 5 minutes.
Meanwhile, cut the onions into thin strips.
In a bowl, add the table cream, the mustard and the salt, mix well and set aside.
In a skillet, add the oil and the onion strips, stir well until slightly golden brown.
Add the crushed garlic cloves and stir.
Add the pieces of liver, previously drained, stir, and let it all cook for 5 minutes.
After this indicated time, add the sauce we made and stir.
Season with 1 pinch of salt, the black pepper, and stir.
Cover the skillet and let it all cook for 15 minutes.
Serve.