Preheat oven to 400 degrees Fahrenheit. Roast the 3 bone marrow bones in the oven, being sure to put in a lipped pan to collect the fat! Roast bone for 45 minutes or until nice and golden brown. Once the bones are roasted, add the rendered beef fat to a heavy bottom pot or a Dutch oven over medium, saving the bones for later in the recipe. Add sliced onions and some salt and start to sweat the onion. We’re not looking for any color. Once the onions start to soften, place a lid on the pot and cook for 45 minutes or until the onions are really soft and tender, stirring every 10-15 minutes. This step is very important to help the onions caramelize more evenly.

After onions are soft, remove the lid. There will be some liquid from the onions, which is fine. Now lower the heat to low and start to caramelize the onions (this will take from 2-4 hours). Stir every few minutes to prevent sticking. It’s worth it. Put on some music and enjoy some adult beverages! You want the onions to break down and become a paste and no longer resemble onions (the steaming of the onions helps this). Once the onions are dark, rich, and sweet, add the thyme bundle, the 3 reserved bones, and the beef stock, cook over medium-low heat and let simmer for 2 more hours (the bones will add a richness and help the beef stock). The soup should be a dark brown. After 2 hours, add salt to taste and a liberal amount of pepper to the soup. Lower heat to low to keep soup warm and remove the thyme bundle and bones.

To finish the dish, crank oven to 450 degrees Fahrenheit. Roast the remaining marrow bones seasoned with salt and pepper on a lipped sheet pan in the oven for about 10 minutes or until the center of the marrow is soft, but not rendered away. You can check with a cake tester or a paring knife (insert into marrow for ten seconds; if the tester is warm to the touch, you are good to go). Be careful, there will be fat in the pan. Save this fat to either top the toasting bread for the soup or reserve in your fridge to roast potatoes or even use for a beef fat hollandaise to complement a nice steak or prime rib! Next, brush olive oil or the reserved beef fat, salt, and pepper on the bread and toast in the oven until crisp but still a bit soft, maybe 5 minutes. Place in a warm bowl on the side.

To serve, in a warm bowl, place the roasted bone marrow in the middle, ladle the soup around the bone, give it a few more cranks of pepper and some fresh thyme. Have some small knives to scoop out the bone marrow and place on the bread and dip in the soup. Enjoy!