01 - Preheat the oven to 425°F.
02 - Arrange marrow bones, cut side up, on a baking tray lined with parchment paper or foil.
03 - Sprinkle sea salt, black pepper, and thyme evenly over the bones.
04 - Roast the bones for 20 to 25 minutes, until the marrow is bubbling and softened but not melted away.
05 - Mix chopped parsley, finely diced shallot, and lemon juice in a small bowl.
06 - Remove bones from oven and let them cool for 2 to 3 minutes.
07 - Serve hot, topped with the parsley garnish. Optionally, scoop marrow onto toasted bread.