2-8 hours before cooking (or overnight), soak the liver in milk (so it's mostly covered) to help remove some of the iron taste.

Before cooking, pat the liver dry with paper towel and season with salt and pepper on both sides.

In a large skillet, cook the bacon over medium-high heat. When the fat begins rendering, add the onions.

Cook the onions until soft and translucent, then transfer the onion and bacon to a bowl and set aside.

Add the cooking fat to the pan (if needed), followed by the liver.

Sear the liver on the first side for 5 minutes, then flip and cook for another 5 minutes until it's nicely browned.

While the liver is cooking, prepare a quick roux for the gravy by combining the flour and butter together in a small dish.

Remove the liver from the pan and keep warm in the oven. Meanwhile, over medium heat, add the stock to the pan and deglaze, scraping the crispy bits.

When the stock begins to bubble, stir in the roux. Once the roux is mixed in, return the onions and bacon to the pan and season with the mustard, salt and pepper.

Taste the sauce and make any adjustments as needed. As the gravy bubbles, it will thicken. At this point, add the cream (if desired), check the seasoning and let it simmer once more until thickened to your desired consistency.

Smother the liver with the gravy, bacon and onions. Serve immediately.