Start by rinsing the liver under cold water and patting it completely dry with paper towels. If there are any visible membranes or tough pieces, trim them away.

Cut the liver into serving-sized pieces. Don't make them too small because they'll shrink slightly during cooking. Set them aside while you prepare the other ingredients.

If you're sensitive to the flavor of liver, you can soak it in milk for 30 minutes beforehand. I do this sometimes, and it definitely creates a milder flavor.

Place a large skillet over medium heat and add the chopped bacon.

Cook for about 8 to 10 minutes, stirring occasionally, until the bacon becomes crispy and golden brown. You'll notice a lot of flavorful bacon fat collecting in the pan.

Transfer the cooked bacon to a plate lined with paper towels, leaving about 2 tablespoons of the bacon drippings in the skillet.

Add the butter to the skillet with the reserved bacon drippings.

Add the sliced onions and cook over medium-low heat for about 12 to 15 minutes. Stir occasionally as they soften and slowly develop a golden color.

The onions should become soft, fragrant, and slightly caramelized. Don't rush this part. The sweetness from the onions helps balance the stronger flavor of the liver.

Increase the heat to medium-high and add the olive oil.

Place the liver pieces into the skillet in a single layer. Cook for about 1 minute per side. You're not trying to cook them completely at this stage.

The goal is simply to create a little color on the outside while keeping the inside mostly uncooked. The first time I made this recipe, I browned the liver too much and it became slightly chewy later. A quick sear works much better.

Transfer the liver to a plate.

Sprinkle the flour over the onions and stir constantly for about 1 minute.

Gradually pour in the beef broth while stirring. Continue stirring until the mixture becomes smooth and starts to thicken slightly.

Add the Worcestershire sauce, thyme, salt, and pepper. Let the sauce simmer gently for 3 to 4 minutes.

At this point, the sauce should lightly coat the back of a spoon without becoming overly thick.

Preheat your oven to 325°F.

Place the liver pieces in the casserole dish. Scatter the cooked bacon evenly over the top.

Pour the onion and broth mixture over everything, making sure the liver is mostly covered.

Use a spoon to gently distribute the onions and sauce throughout the dish.

Cover the casserole dish tightly with aluminum foil.

After 40 minutes, remove the foil and continue baking for another 10 to 15 minutes.

The sauce should be bubbling around the edges, and the liver should be tender when pierced with a fork.

Remove the casserole from the oven and allow it to rest for about 10 minutes.

Sprinkle fresh parsley over the top before serving.

The resting period helps the sauce settle and allows the flavors to blend together even more.