Roasted Bone Marrow Recipe

Prepare onions

Peel and thinly slice the yellow onions to yield about 2 cups. Use a sharp knife or mandoline for even slices.

Heat a heavy skillet over medium heat. Add the butter and olive oil and let the butter melt and foam but not brown.

Add the sliced onions and sprinkle the sugar over them. Stir to coat and spread the onions evenly in the pan. Cook, stirring occasionally, adjusting heat so the onions soften and begin to caramelize but do not burn—about 15–20 minutes. If they brown too quickly, reduce heat.

Once the onions are deeply golden and softened, add the balsamic vinegar and red wine (or beef stock). Scrape up any browned bits from the pan and continue to cook until most of the liquid is reduced and the mixture is jammy—about 5–7 minutes.

Stir in the thyme leaves, salt, and 1/2 tsp freshly ground black pepper. Taste and adjust seasoning. Remove from heat and set aside in a small bowl; the jam can be kept warm or at room temperature while you roast the marrow.

Preheat your oven to 425°F (220°C). Line a rimmed baking sheet with foil for easy cleanup and place a wire rack or folded foil rolls to steady the bones upright if needed.

Rinse the marrow bones briefly under cold water and pat dry with paper towels. Use a small knife to remove any bone fragments or loose bits of marrow on the surface.

Arrange the marrow bones cut side up on the prepared baking sheet so the marrow is visible. Season each exposed marrow surface lightly with 2 tsp kosher salt divided evenly among bones and with the 1 tsp freshly ground black pepper divided evenly (about a light pinch per bone).

Roast in the preheated oven until the marrow is soft and just beginning to bubble at the edges but not rendering away completely, about 15–20 minutes depending on bone size. The marrow should be glossy and soft but still hold shape.

While the bones roast, toast the country bread slices until crisp and warm. Keep them warm.

Remove the bones from the oven. Let them rest 1–2 minutes so the marrow firms slightly but remains spoonable. Using a small spoon or marrow spoon, scoop the marrow into small bowls or directly onto toasted bread.

Top each spoonful or toast with about 1–2 tablespoons of the bittersweet onion jam. Sprinkle the chopped parsley over the marrow and jam, and finish each with a light squeeze of lemon if desired to cut the richness.

Serve immediately with extra toasted bread and lemon wedges on the side.