1. Optional roast (recommended for depth)
   Place the marrow bones on a roasting tray and roast at 220°C fan for 25–30 minutes, until lightly browned. This adds savoury depth but can be skipped for a lighter stock.
2. Transfer the bones to a large stockpot and add the vegetables, bay leaf, peppercorns and parsley stalks.
3. Cover with cold water so everything is submerged by 3–4cm (around 3 litres).
4. Bring slowly to a bare simmer. Skim off any grey foam that rises.
5. Reduce the heat so the stock barely trembles and cook uncovered for 4–5 hours. Do not boil.
6. Strain through a fine sieve into a clean container. Discard the vegetables.
7. Cool quickly, then refrigerate. Once chilled, lift off excess surface fat if you want a lighter stock.

Multi-Cooker Option (Ninja Foodi MAX)

1. Optional roast the bones as above for extra depth, or skip straight to the pot for a lighter stock.
2. Place the bones, vegetables, bay, peppercorns and parsley stalks into the Foodi pot.
3. Add cold water to the MAX fill line (do not exceed).
4. Select Pressure → High and cook for 90 minutes.
5. Allow a full natural pressure release (about 20–30 minutes).
6. Carefully open the lid, then switch to Sauté → Low and simmer uncovered for 30–45 minutes to concentrate the stock slightly.
7. Strain through a fine sieve and cool quickly.