Roast the marrow bones

• Spread the marrow bones on a parchment-lined baking tray.
• Roast until the marrow is soft and the fat has rendered out.

Scoop out the marrow

• Scoop the marrow out of the bones into a bowl.
• Pour in the dripped oils and rendered tallow from the tray.

Chill the marrow

• Cool in the fridge until firm.

Whip until light

• Whip with a mixer until soft peaks form and the texture turns light and buttery.

Store and serve

• Keep in the fridge for about a week or freeze for up to six months.
• Thaw at room temperature before serving.
• Spoon-feed directly or mix into food; for adults, spread on toast and sprinkle with flaky salt.